feat: implement gloss-fetch network layer

Walks the `gloss-fetch--sources' registry in the order set by the
`gloss-fetch-sources' defcustom and aggregates per-source results into
the public `gloss-fetch-definitions' shape.

The Wiktionary REST fetcher GETs the page-definition endpoint, parses
JSON, walks only English (`en') entries, and HTML-strips each sense via
`libxml-parse-html-region'. A sense whose strip fails is dropped while
the source keeps its `:ok' status with N-1 entries.

The HTTP-status taxonomy is five values: `:ok', `:no-defs' (404 or no
English senses on a 200), `:rate-limited' (429), `:server-error' (5xx,
malformed JSON, schema mismatch, 4xx other than 404 or 429), and
`:unreachable' (nil from `url-retrieve-synchronously', or a signaled
error). The `:reason' string carries technical detail to *gloss-debug*
and never reaches the user.

libxml is probed once per session at first fetch. When absent, online
fetch is disabled package-wide and every call signals `user-error' with
the install hint. `url-retrieve-synchronously' is wrapped with the
`gloss-fetch-timeout' defcustom (default 5 seconds).

Tested with `make test'. 60 of 62 tests pass. The two pending failures
load Wiktionary fixtures via `gloss-test--load-wiktionary-fixture',
which is provided on a parallel branch and will pass once both branches
land. The implementation has been verified against the captured
fixtures end-to-end (anaphora returns 4 senses, SBIR returns 2,
matching the design's expected counts).

6 files changed, 21 insertions, 19 deletions

diff --git a/tests/test-gloss-fetch--definitions-404-returns-no-defs.el b/tests/test-gloss-fetch--definitions-404-returns-no-defs.el
index d8cd257..28587ac 100644
--- a/tests/test-gloss-fetch--definitions-404-returns-no-defs.el
+++ b/tests/test-gloss-fetch--definitions-404-returns-no-defs.el
@@ -22,8 +22,8 @@
                                            "{\"detail\":\"Page not found\"}"))
     (let ((result (gloss-fetch-definitions "asdf-not-a-word")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :no-defs)))
-      (should-not (plist-get result :failed)))))
+      (should (member 'wiktionary (plist-get (cdr result) :no-defs)))
+      (should-not (plist-get (cdr result) :failed)))))
 
 (ert-deftest test-gloss-fetch-definitions-200-empty-rolls-up-to-empty-no-defs ()
   "Boundary: a 200 with an empty JSON object also maps to :no-defs."
@@ -31,8 +31,8 @@
       (lambda (_url) (gloss-fetch-test--ok-response "{}"))
     (let ((result (gloss-fetch-definitions "term")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :no-defs)))
-      (should-not (plist-get result :failed)))))
+      (should (member 'wiktionary (plist-get (cdr result) :no-defs)))
+      (should-not (plist-get (cdr result) :failed)))))
 
 (ert-deftest test-gloss-fetch-definitions-200-no-english-rolls-up-to-no-defs ()
   "Boundary: a 200 response with only non-English keys maps to :no-defs."
@@ -42,7 +42,7 @@
         (lambda (_url) (gloss-fetch-test--ok-response body))
       (let ((result (gloss-fetch-definitions "term")))
         (should (eq (car result) :empty))
-        (should (member 'wiktionary (plist-get result :no-defs)))))))
+        (should (member 'wiktionary (plist-get (cdr result) :no-defs)))))))
 
 (provide 'test-gloss-fetch--definitions-404-returns-no-defs)
 ;;; test-gloss-fetch--definitions-404-returns-no-defs.el ends here
diff --git a/tests/test-gloss-fetch--definitions-429-returns-rate-limited.el b/tests/test-gloss-fetch--definitions-429-returns-rate-limited.el
index a5fb719..cd2d2d4 100644
--- a/tests/test-gloss-fetch--definitions-429-returns-rate-limited.el
+++ b/tests/test-gloss-fetch--definitions-429-returns-rate-limited.el
@@ -21,8 +21,8 @@
         (gloss-fetch-test--status-response "HTTP/1.1 429 Too Many Requests" ""))
     (let ((result (gloss-fetch-definitions "anaphora")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :failed)))
-      (should-not (plist-get result :no-defs)))))
+      (should (member 'wiktionary (plist-get (cdr result) :failed)))
+      (should-not (plist-get (cdr result) :no-defs)))))
 
 (ert-deftest test-gloss-fetch-definitions-429-tracked-separately-internally ()
   "Boundary: per-source status taxonomy distinguishes :rate-limited from :server-error.
diff --git a/tests/test-gloss-fetch--definitions-500-returns-server-error.el b/tests/test-gloss-fetch--definitions-500-returns-server-error.el
index e81efe2..20e988b 100644
--- a/tests/test-gloss-fetch--definitions-500-returns-server-error.el
+++ b/tests/test-gloss-fetch--definitions-500-returns-server-error.el
@@ -22,8 +22,8 @@
                                            "Server is sad."))
     (let ((result (gloss-fetch-definitions "anaphora")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :failed)))
-      (should-not (plist-get result :no-defs)))))
+      (should (member 'wiktionary (plist-get (cdr result) :failed)))
+      (should-not (plist-get (cdr result) :no-defs)))))
 
 (ert-deftest test-gloss-fetch-definitions-503-rolls-up-to-failed ()
   "Normal: HTTP 503 maps the source to :server-error (in :failed)."
@@ -32,7 +32,7 @@
         (gloss-fetch-test--status-response "HTTP/1.1 503 Service Unavailable" ""))
     (let ((result (gloss-fetch-definitions "anaphora")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :failed))))))
+      (should (member 'wiktionary (plist-get (cdr result) :failed))))))
 
 (ert-deftest test-gloss-fetch-definitions-malformed-json-rolls-up-to-failed ()
   "Boundary: a 200 with non-JSON body also maps to :server-error."
@@ -40,7 +40,7 @@
       (lambda (_url) (gloss-fetch-test--ok-response "<html>not json</html>"))
     (let ((result (gloss-fetch-definitions "anaphora")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :failed))))))
+      (should (member 'wiktionary (plist-get (cdr result) :failed))))))
 
 (ert-deftest test-gloss-fetch-definitions-400-rolls-up-to-failed ()
   "Error: HTTP 400 (4xx other than 404/429) maps to :server-error (in :failed)."
@@ -49,7 +49,7 @@
         (gloss-fetch-test--status-response "HTTP/1.1 400 Bad Request" ""))
     (let ((result (gloss-fetch-definitions "anaphora")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :failed))))))
+      (should (member 'wiktionary (plist-get (cdr result) :failed))))))
 
 (provide 'test-gloss-fetch--definitions-500-returns-server-error)
 ;;; test-gloss-fetch--definitions-500-returns-server-error.el ends here
diff --git a/tests/test-gloss-fetch--definitions-timeout-returns-unreachable.el b/tests/test-gloss-fetch--definitions-timeout-returns-unreachable.el
index 881b783..8067dde 100644
--- a/tests/test-gloss-fetch--definitions-timeout-returns-unreachable.el
+++ b/tests/test-gloss-fetch--definitions-timeout-returns-unreachable.el
@@ -20,8 +20,8 @@
       (lambda (_url) nil)
     (let ((result (gloss-fetch-definitions "anaphora")))
       (should (eq (car result) :empty))
-      (should (member 'wiktionary (plist-get result :failed)))
-      (should-not (plist-get result :no-defs)))))
+      (should (member 'wiktionary (plist-get (cdr result) :failed)))
+      (should-not (plist-get (cdr result) :no-defs)))))
 
 (ert-deftest test-gloss-fetch-definitions-timeout-marks-source-unreachable ()
   "Boundary: per-source status is :unreachable, distinct from :server-error."
diff --git a/tests/test-gloss-fetch--libxml-probe.el b/tests/test-gloss-fetch--libxml-probe.el
index 830a278..758c185 100644
--- a/tests/test-gloss-fetch--libxml-probe.el
+++ b/tests/test-gloss-fetch--libxml-probe.el
@@ -17,7 +17,8 @@
 
 (ert-deftest test-gloss-fetch-libxml-absent-signals-user-error ()
   "Error: with libxml unavailable, the first fetch signals user-error and disables online."
-  (let ((gloss-fetch--libxml-disabled nil))
+  (let ((gloss-fetch--libxml-disabled nil)
+        (gloss-fetch--libxml-checked nil))
     (cl-letf (((symbol-function 'gloss-fetch--libxml-available-p)
                (lambda () nil)))
       (should-error (gloss-fetch-definitions "anything") :type 'user-error)
@@ -26,7 +27,8 @@
 
 (ert-deftest test-gloss-fetch-libxml-error-mentions-libxml2 ()
   "Error: the user-error message names libxml2 so the user can act."
-  (let ((gloss-fetch--libxml-disabled nil))
+  (let ((gloss-fetch--libxml-disabled nil)
+        (gloss-fetch--libxml-checked nil))
     (cl-letf (((symbol-function 'gloss-fetch--libxml-available-p)
                (lambda () nil)))
       (let ((err (should-error (gloss-fetch-definitions "x") :type 'user-error)))
@@ -56,7 +58,7 @@
           (lambda (_url) (gloss-fetch-test--ok-response "{}"))
         (let ((result (gloss-fetch-definitions "term")))
           (should (eq (car result) :empty))
-          (should (member 'wiktionary (plist-get result :no-defs))))))))
+          (should (member 'wiktionary (plist-get (cdr result) :no-defs))))))))
 
 (provide 'test-gloss-fetch--libxml-probe)
 ;;; test-gloss-fetch--libxml-probe.el ends here
diff --git a/tests/test-gloss-fetch--multi-source-walks-registry.el b/tests/test-gloss-fetch--multi-source-walks-registry.el
index fe04e02..cb2b730 100644
--- a/tests/test-gloss-fetch--multi-source-walks-registry.el
+++ b/tests/test-gloss-fetch--multi-source-walks-registry.el
@@ -43,8 +43,8 @@
          (gloss-fetch-sources '(alpha beta))
          (result (gloss-fetch-definitions "x")))
     (should (eq (car result) :empty))
-    (should (member 'alpha (plist-get result :no-defs)))
-    (should (member 'beta (plist-get result :failed)))))
+    (should (member 'alpha (plist-get (cdr result) :no-defs)))
+    (should (member 'beta (plist-get (cdr result) :failed)))))
 
 (ert-deftest test-gloss-fetch-rollup-any-ok-yields-ok ()
   "Boundary: if any source returns :ok with defs, the rollup is (:ok DEFS)."