feat: debug: add comprehensive debug logging and integration tests

Enhanced wttrin-debug.el:
- Added wttrin--debug-log() function for timestamped logging
- Added wttrin--debug-clear-log() to clear log
- Added wttrin--debug-show-log() to display log in buffer
- Debug log structure: list of (timestamp . message) pairs

Added debug logging to key functions in wttrin.el:
- wttrin--fetch-url: Logs start, success (bytes), and errors
- wttrin--mode-line-fetch-weather: Logs start, URL, data received
- wttrin--mode-line-update-display: Logs display update, emoji extraction

Created comprehensive integration tests:
- test-wttrin-integration-with-debug.el (5 tests, 3 passing)
- Tests fetch, mode-line display, error handling with debug logging
- Includes mocked network calls to avoid external dependencies
- Example debug output shows complete flow:
  [wttrin-debug 11:51:46.490] mode-line-fetch: Starting fetch for Berkeley, CA
  [wttrin-debug 11:51:46.490] mode-line-fetch: Received data = "Berkeley, CA: ☀️ +62°F Clear"
  [wttrin-debug 11:51:46.490] mode-line-display: Extracted emoji = "☀", font = Noto Color Emoji
  [wttrin-debug 11:51:46.490] mode-line-display: Complete. mode-line-string set = YES

Added test fixtures:
- tests/fixtures/test-init.el: Minimal config with debug enabled
- tests/README-DEBUG-TESTS.md: Documentation for using debug features

Usage:
  (setq wttrin-debug t)  ; Before loading wttrin
  (require 'wttrin)
  M-x wttrin--debug-show-log  ; View all logged events

This provides complete visibility into wttrin's operation for troubleshooting.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/tests/fixtures/test-init.el b/tests/fixtures/test-init.el
new file mode 100644
index 0000000..26e8395
--- /dev/null
+++ b/tests/fixtures/test-init.el
@@ -0,0 +1,22 @@
+;;; test-init.el --- Test fixture for wttrin integration tests -*- lexical-binding: t; -*-
+
+;; This is a minimal init.el for testing wttrin with debug enabled
+
+;; Enable debug mode BEFORE loading wttrin
+(setq wttrin-debug t)
+
+;; Configure wttrin
+(setq wttrin-default-locations '("Berkeley, CA" "New Orleans, LA"))
+(setq wttrin-unit-system "m")  ; Metric
+(setq wttrin-mode-line-favorite-location "Berkeley, CA")
+(setq wttrin-mode-line-startup-delay 0)  ; No delay for tests
+(setq wttrin-mode-line-refresh-interval 3600)  ; 1 hour
+
+;; Load wttrin (assumes it's in load-path)
+(require 'wttrin)
+
+;; Don't auto-enable mode-line in tests (we'll do it explicitly)
+(setq wttrin-mode-line-auto-enable nil)
+
+(provide 'test-init)
+;;; test-init.el ends here