refactor(load-graph): make hidden module dependencies explicit

Phase 2 of the load-graph project. I fixed the seven hidden dependencies the classification surfaced, so each module declares what it uses instead of relying on init order.

- system-defaults now requires host-environment and user-constants at runtime. They were eval-when-compile only, but env-bsd-p and user-home-dir are read at load, so the compiled module couldn't load standalone.
- custom-buffer-file, dev-fkeys, calendar-sync, and video-audio-recording require keybindings and drop their (when (boundp 'cj/custom-keymap) ...) shims. The shim silently dropped the C-; binding when the module loaded before keybindings. The explicit require makes the dependency real.
- flycheck-config and mail-config require keybindings for their cj/custom-keymap bindings (a use-package :map and a direct keymap-set).
- Removed a dead eval-when-compile (defvar cj/custom-keymap) in transcription-config; nothing there used the variable.

No init.el load-order change. keybindings and the foundation modules already load before these, so the requires are no-ops at startup and only fix standalone and test loading.

I verified each fix with a fresh emacs --batch (require 'X), then swept all modules standalone: every one loads or fails only with a clear missing-package message. Full make test, make validate-modules, and an init smoke all pass. Module headers and the inventory's hidden-dependency section are updated to mark the seven resolved.

1 files changed, 4 insertions, 7 deletions

diff --git a/modules/video-audio-recording.el b/modules/video-audio-recording.el
index 38c1931c..cec5df85 100644
--- a/modules/video-audio-recording.el
+++ b/modules/video-audio-recording.el
@@ -10,10 +10,8 @@
 ;;   run only on command (command-loaded target).
 ;; Top-level side effects: defines cj/record-map and conditionally registers it
 ;;   under C-; r.
-;; Runtime requires: system-lib. keybindings is needed for the C-; r binding but
-;;   only reached through a boundp guard, so the binding silently drops
-;;   standalone. Phase 2 fix.
-;; Direct test load: conditional (C-; r registration skipped without keybindings).
+;; Runtime requires: system-lib, keybindings.
+;; Direct test load: yes (requires keybindings explicitly).
 ;;
 ;; Desktop video and audio recording from within Emacs using ffmpeg.
 ;; Records from both microphone and system audio simultaneously, which
@@ -109,6 +107,7 @@
 ;;; Code:
 
 (require 'system-lib)
+(require 'keybindings)  ;; provides cj/custom-keymap
 
 ;;; ============================================================
 ;;; Configuration Variables
@@ -1089,9 +1088,7 @@ Changes take effect on the next recording (not the current one)."
     map)
   "Keymap for video/audio recording operations under C-; r.")
 
-;; Only bind keys when running interactively (not in batch/test mode)
-(when (boundp 'cj/custom-keymap)
-  (keymap-set cj/custom-keymap "r" cj/record-map))
+(keymap-set cj/custom-keymap "r" cj/record-map)
 
 (with-eval-after-load 'which-key
   (which-key-add-key-based-replacements