feat(skill): port debrief to a Claude Code Skill (zero-install)

examples/sample-output.md

@@ -0,0 +1,128 @@
+# Sample outputs
+
+Reference outputs the skill should produce given a representative day. Use these as regression anchors when iterating on SKILL.md wording.
+
+---
+
+## Example 1 — Full four-bucket day
+
+**Ask:** `debrief today`
+
+**Output:**
+
+```
+Fri, Apr 18 2026
+
+Decided
+  - Went with go-yaml over mapstructure — reflection cost wasn't worth the flexibility
+  - Dropped the Slack webhook path for v1 — too much scope
+
+Shipped
+  - Handle PR-squash chore commits (#11)
+  - Redesigned the cost table with per-model breakdown (#12)
+  - Added --project filter to standup and cost commands
+
+Investigated
+  - goreleaser's default matrix skips arm64 Linux — had to add it explicitly
+
+Watch
+  - The classifier regex is too aggressive on test: prefixes and might drop real work
+```
+
+Note: **Decided** and **Investigated** bullets come from Claude session notes. **Shipped** bullets are a mix of commits and session notes about completed work. **Watch** captures a risk the user flagged during a session but didn't file as an issue.
+
+---
+
+## Example 2 — Quiet day (chore-only)
+
+**Ask:** `debrief today`
+
+**Commits:** only `chore: bump deps`, `chore: format`, `test: flaky retry`.
+
+**Session notes:** none survived the filter (all were planning language).
+
+**Output:**
+
+```
+Quiet day — just chores and lints. Nothing shipped worth writing up.
+```
+
+This exact line signals "the tool worked, your day was just quiet" — distinct from "the tool found nothing" (which means a broken scan).
+
+---
+
+## Example 3 — Nothing at all
+
+**Ask:** `debrief yesterday` on a day the user didn't work.
+
+**Output:**
+
+```
+No activity to report.
+```
+
+---
+
+## Example 4 — Slack format
+
+**Ask:** `debrief today as slack`
+
+**Output:**
+
+````
+`Fri, Apr 18 2026`
+
+- Went with go-yaml over mapstructure — reflection cost wasn't worth the flexibility
+- Handle PR-squash chore commits (#11)
+- goreleaser's default matrix skips arm64 Linux — had to add it explicitly
+- The classifier regex is too aggressive on test: prefixes and might drop real work
+````
+
+- Date is wrapped in backticks (Slack renders it as inline code).
+- No section headers — flat list.
+- Bucket order is preserved in bullet order.
+
+---
+
+## Example 5 — Week range
+
+**Ask:** `debrief this week`
+
+**Output:**
+
+```
+Week of Apr 13 – Apr 19, 2026
+
+Decided
+  - Went with go-yaml over mapstructure
+  - Dropped cost subcommand — claudecost owns pricing
+
+Shipped
+  - Handle PR-squash chore commits (#11)
+  - Humanizer visibility banner (#9)
+  - CWD-fallback git discovery (#10)
+  - Cost table redesign with per-model breakdown (#12)
+
+Investigated
+  - goreleaser arm64 Linux matrix gap
+  - GIT_* env vars override -C flag in subprocesses
+
+Watch
+  - Classifier aggressive on test: prefixes
+```
+
+For multi-day ranges, bullets are deduplicated and merged across days. Date header is a range, not a single day.
+
+---
+
+## What "good output" means — tuning rubric
+
+When dogfooding, grade each day's output against these questions:
+
+1. **Could I paste this into Slack verbatim?** If no — the wording is off.
+2. **Does every bullet describe real work I did?** If no — the note filter let noise through.
+3. **Is anything I actually did missing?** If yes — either the filter is too strict, or the commit was covered-by-notes incorrectly.
+4. **Did Decided/Investigated/Watch bullets land in the right buckets?** If a "decided" showed up in Shipped — the keyword list missed it.
+5. **On a chore-only day, does it say "Quiet day"?** If it says "No activity" — the noise-vs-emptiness distinction broke.
+
+Fix the SKILL.md wording — don't add code.

internal/collector/git_test.go

@@ -31,10 +31,44 @@ func sanitizedEnv() []string {
 	return out
 }
 
+// unsetGitHookVars unsets process-level GIT_* variables that git sets when
+// running inside a hook (e.g. pre-commit). sanitizedEnv only scrubs env for
+// subprocesses we launch directly — the production collector code under test
+// spawns its own git processes that inherit os.Environ(), so those still see
+// the leaked GIT_DIR/GIT_WORK_TREE and target the outer worktree instead of
+// the temp repo. Unset at the process level and restore via t.Cleanup.
+func unsetGitHookVars(t *testing.T) {
+	t.Helper()
+	hookVars := []string{
+		"GIT_DIR",
+		"GIT_WORK_TREE",
+		"GIT_INDEX_FILE",
+		"GIT_COMMON_DIR",
+		"GIT_PREFIX",
+		"GIT_EXEC_PATH",
+		"GIT_REFLOG_ACTION",
+	}
+	for _, k := range hookVars {
+		old, present := os.LookupEnv(k)
+		if !present {
+			continue
+		}
+		if err := os.Unsetenv(k); err != nil {
+			t.Fatalf("unset %s: %v", k, err)
+		}
+		t.Cleanup(func() {
+			_ = os.Setenv(k, old)
+		})
+	}
+}
+
 func TestGitCollector_CollectFromTempRepo(t *testing.T) {
 	if _, err := exec.LookPath("git"); err != nil {
 		t.Skip("git not available")
 	}
+	// See unsetGitHookVars — required when the test runs inside a pre-commit
+	// hook so Collect() targets the temp repo, not the outer worktree.
+	unsetGitHookVars(t)
 
 	// Create a temp repo with commits.
 	dir := t.TempDir()
@@ -58,7 +92,13 @@ func TestGitCollector_CollectFromTempRepo(t *testing.T) {
 	}
 
 	run("init")
-	run("checkout", "-b", "main")
+	// Disable any global hooksPath — the temp repo inherits ~/.gitconfig
+	// settings; a developer-machine commit-msg hook (e.g. min-length) would
+	// otherwise fire inside the test.
+	run("config", "core.hooksPath", "/dev/null")
+	// -B (create-or-reset) tolerates init.defaultBranch=main, which makes
+	// git init pre-create "main" and then reject -b main.
+	run("checkout", "-B", "main")
 	// Belt-and-suspenders: also set identity via repo-local config so commits
 	// resolve to test@example.com even if GIT_AUTHOR_* env doesn't propagate.
 	run("config", "user.email", "test@example.com")
@@ -159,6 +199,8 @@ func TestGitCollector_MultiDayCommitsSplitByDay(t *testing.T) {
 	if _, err := exec.LookPath("git"); err != nil {
 		t.Skip("git not available")
 	}
+	// See TestGitCollector_CollectFromTempRepo for why this is needed.
+	unsetGitHookVars(t)
 
 	dir := t.TempDir()
 	repo := filepath.Join(dir, "multi-day-project")
@@ -186,7 +228,9 @@ func TestGitCollector_MultiDayCommitsSplitByDay(t *testing.T) {
 	)
 
 	run(baseEnv, "init")
-	run(baseEnv, "checkout", "-b", "main")
+	// See TestGitCollector_CollectFromTempRepo for the rationale on these.
+	run(baseEnv, "config", "core.hooksPath", "/dev/null")
+	run(baseEnv, "checkout", "-B", "main")
 	run(baseEnv, "config", "user.email", "test@example.com")
 	run(baseEnv, "config", "user.name", "Test User")