refactor(foundation): hygiene pass across early-init, user-constants, system-defaults, chrono-tools

Six small fixes the 2026-05-15 module-by-module re-review surfaced:

- Consolidate `user-home-dir` -- canonical defconst stays in
  early-init.el (package-archive bootstrap needs it before normal
  modules load); user-constants.el switches to a `defvar` with the
  identical `(getenv "HOME")` expression so the module still loads /
  byte-compiles standalone, but at runtime early-init's defconst
  wins.
- Drop the redundant `(autoload 'env-bsd-p ...)` line in
  system-defaults.el.  The `(eval-when-compile (require
  'host-environment))` already exposes the symbol to the byte
  compiler, and at runtime host-environment is loaded earlier in
  init.el.  Added a comment documenting the boundary.
- Convert `cj/debug-modules` and `cj/use-online-repos` from `defvar`
  to `defcustom`, with `:type`, `:group 'cj`, and a top-level
  `(defgroup cj ...)` so both show up in M-x customize.
- Name the package-archive priorities in early-init.el.  Nine new
  defconsts replace the magic numbers (200 / 125 / 120 / 115 / 100 /
  25 / 20 / 15 / 5) with one constant each, plus a header comment
  explaining the local-first ordering and the gnu > nongnu > melpa >
  melpa-stable trust ranking within each tier.
- Delete the 19-line commented-out `use-package time` world-clock
  block in chrono-tools.el.  `time-zones` immediately above is the
  active replacement; git history preserves the old config if anyone
  needs it.
- Add coverage for `cj/tmr-select-sound-file`.  Collapsed the
  prefix-arg branch into a delegation to
  `cj/tmr-reset-sound-to-default` (single reset source) and
  extracted `cj/tmr--available-sound-files` as a pure helper that
  tests directly.  9 ERT tests across Normal / Boundary / Error
  cover the available-sounds helper, the reset path, the prefix-arg
  delegation (no prompt), the normal selection path, and the
  empty-dir / missing-dir / cancel boundaries.

1 files changed, 18 insertions, 6 deletions

diff --git a/modules/user-constants.el b/modules/user-constants.el
index 21e141a5..2cc4a50c 100644
--- a/modules/user-constants.el
+++ b/modules/user-constants.el
@@ -22,12 +22,15 @@
 
 ;; -------------------------------- Debug Toggle -------------------------------
 
-(defvar cj/debug-modules nil
+(defcustom cj/debug-modules nil
   "List of modules with debug functions enabled.
-Possible values: org-agenda, mail, chime, etc.
 Set to t to enable all debug modules.
-Example: (setq cj/debug-modules '(org-agenda mail))
-         (setq cj/debug-modules t)  ; Enable all")
+Set to a list of module symbols (e.g. \\='(org-agenda mail)) to enable
+debug output for those modules only.  Possible values: org-agenda,
+mail, chime, etc."
+  :type '(choice (const :tag "All modules" t)
+                 (repeat :tag "Specific modules" symbol))
+  :group 'cj)
 
 ;; -------------------------------- Contact Info -------------------------------
 
@@ -71,8 +74,17 @@ the regular transcription pipeline.")
 (defconst emacs-early-init-file (expand-file-name "early-init.el" user-emacs-directory)
   "The location of Emacs's early init file.")
 
-(defconst user-home-dir (getenv "HOME")
-  "The user's home directory per the environment variable.")
+;; Canonical definition of `user-home-dir' lives in `early-init.el' so
+;; the package-archive paths there can reference it during package
+;; bootstrap.  The `defvar' below is a no-op at runtime (early-init's
+;; defconst wins, defvar doesn't reassign a bound symbol) -- it exists
+;; only so this module loads / byte-compiles standalone, when
+;; early-init hasn't run.  If you ever change the expression here, keep
+;; it identical to early-init.el's.
+(defvar user-home-dir (getenv "HOME")
+  "The user's home directory per the environment variable.
+Canonical definition in early-init.el; this form is a standalone-load
+fallback only.")
 
 (defconst books-dir (expand-file-name "sync/books/" user-home-dir)
   "The location of book files for CalibreDB.")