refactor: switch gloss-fetch result to uniform plist shapeHEADmain

The previous shape (:ok DEFS) | (:empty :no-defs (...) :failed (...)) was malformed as a plist. The :empty tag at position 0 shifted the plist alignment. plist-get on :no-defs or :failed returned nil. Tests had to use (plist-get (cdr result) ...) as a workaround.

The new shape is a uniform plist with all three keys always present: (:defs DEFS :no-defs (SYM ...) :failed (SYM ...)). Consumers branch on whether :defs is non-empty. There is no tag. plist-get works uniformly across success and empty cases.

Updated gloss-fetch.el (rollup function and docstrings), 7 test files, and the design doc (docs/design/gloss.org § Error Handling).

Tested by `make test`. 65 tests pass in 0.36 seconds.

1 files changed, 3 insertions, 3 deletions

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 cd2d2d4..84e6f49 100644
--- a/tests/test-gloss-fetch--definitions-429-returns-rate-limited.el
+++ b/tests/test-gloss-fetch--definitions-429-returns-rate-limited.el
@@ -20,9 +20,9 @@
       (lambda (_url)
         (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 (cdr result) :failed)))
-      (should-not (plist-get (cdr result) :no-defs)))))
+      (should-not (plist-get result :defs))
+      (should (member 'wiktionary (plist-get result :failed)))
+      (should-not (plist-get result :no-defs)))))
 
 (ert-deftest test-gloss-fetch-definitions-429-tracked-separately-internally ()
   "Boundary: per-source status taxonomy distinguishes :rate-limited from :server-error.