ci: replace codecov with local coverage threshold check

Codecov requires an account and token to function. Replace it with
a self-contained `go tool cover` step that fails the build if total
coverage drops below 50% (currently ~58%). This catches test
regressions without external service dependencies.

.github/workflows/go.yml

@@ -43,12 +43,14 @@ jobs:
     - name: Run Tests with Race Detector and Coverage
       run: go test -race -coverprofile=coverage.out ./... -timeout=10m
 
-    - name: Upload Coverage to Codecov
-      uses: codecov/codecov-action@v5
-      with:
-        files: ./coverage.out
-        flags: unittests
-        name: codecov-umbrella
+    - name: Check coverage threshold
+      run: |
+        COVERAGE=$(go tool cover -func=coverage.out | grep '^total:' | awk '{print substr($3, 1, length($3)-1)}')
+        echo "Total coverage: ${COVERAGE}%"
+        if [ "$(echo "$COVERAGE < 50" | bc)" -eq 1 ]; then
+          echo "::error::Coverage ${COVERAGE}% is below 50% threshold"
+          exit 1
+        fi
 
   build:
     name: Build

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- CI: Coverage threshold enforcement — fails build if total coverage drops below 50%
 - CI: Release workflow that automatically builds and uploads Linux/Windows binaries to GitHub Releases on tag push
 - Monthly guild item claim tracking per character per type (standard/HLC/EXC), with schema migration (`31-monthly-items.sql`) adding claim timestamps to the `stamps` table
 - API: `GET /version` endpoint returning server name and client mode (`{"clientMode":"ZZ","name":"Erupe-CE"}`)

docs/technical-debt.md

@@ -59,8 +59,8 @@ These are validated indirectly through mock-based handler tests but have no SQL-
 
 ### 4. CI updates
 
-- ~~`codecov-action@v4` could be updated to `v5` (current stable)~~ **Fixed.** Updated to `codecov-action@v5`.
-- No coverage threshold is enforced — coverage is uploaded but regressions aren't caught
+- ~~`codecov-action@v4` could be updated to `v5` (current stable)~~ **Removed.** Replaced with local `go tool cover` threshold check (no Codecov account needed).
+- ~~No coverage threshold is enforced — coverage is uploaded but regressions aren't caught~~ **Fixed.** CI now fails if total coverage drops below 50% (current: ~58%).
 
 ---
 
@@ -93,4 +93,4 @@ Based on remaining impact:
 1. ~~**Add tests for `handlers_commands.go`**~~ — **Done.** 62 tests covering all 12 commands (ban, timer, PSN, reload, key quest, rights, course, raviente, teleport, discord, playtime, help), disabled-command gating, op overrides, error paths, and `initCommands`.
 2. **Fix bookshelf data pointer** (`model_character.go`) — corrupts saves for three game versions (needs save data validation)
 3. **Fix achievement rank-up notifications** (`handlers_achievement.go:125`) — needs protocol research on `MhfDisplayedAchievement`
-4. **Add coverage threshold** to CI — prevents regressions
+4. ~~**Add coverage threshold** to CI~~ — **Done.** 50% floor enforced via `go tool cover` in CI; Codecov removed.