add in-repo agent skill for working on the tracker project

skills/tracker/SKILL.md documents build/run/vet, layout, and conventions.
Anchor the .gitignore binary pattern to /tracker so the skill dir is tracked.

.gitignore

@@ -1,4 +1,4 @@
-tracker
+/tracker
 tracker.db
 tracker.db-shm
 tracker.db-wal

skills/tracker/SKILL.md

@@ -0,0 +1,76 @@
+---
+name: tracker
+description: >
+  Work on the tracker project — a single-binary Go + SQLite project tracker with
+  server-rendered HTML, bcrypt auth, sessions, and a JSON API. Triggers when
+  editing files under internal/ or main.go, running/building the tracker binary,
+  touching auth or the store, or any request to add a feature or fix a bug in
+  this repo. Use it to keep changes consistent with the existing conventions.
+---
+
+# Tracker Skill
+
+A single-binary project tracker. Go + SQLite (pure-Go driver, no cgo),
+server-rendered templates, no build step and no JS at runtime. Keep changes
+small, match the surrounding style, and rebuild + `go vet` before finishing.
+
+## Build, run, vet
+
+```
+go build -o tracker .      # build the binary
+go vet ./...               # static checks — run after every change
+```
+
+Run it: `./tracker -db <path>` listens on `:8420` by default.
+Create a user: `./tracker -adduser kyle` (prompts for a passphrase, min 8 chars),
+or non-interactively with `TRACKER_PASSWORD=... ./tracker -adduser kyle`.
+Change a passphrase: `./tracker -changepw kyle` (same env-var variant).
+
+There are no automated tests yet. If you add code, verify by building, `go vet`,
+and exercising the binary or the running server manually.
+
+## Layout
+
+- `main.go` — CLI flags (`-db`, `-addr`, `-adduser`, `-changepw`), the
+  interactive passphrase prompts (`golang.org/x/term`), bcrypt hashing.
+- `internal/server/` — HTTP handlers and templates.
+  - `server.go` — `Routes()` wiring, embedded templates/static, page handlers.
+  - `api.go` — JSON API handlers under `/api/v1/`.
+  - `auth.go` — password check, sessions, api keys, auth middleware.
+- `internal/store/` — SQLite access (modernc.org/sqlite, pure Go).
+  - `store.go` — schema/migrate, projects/notes/tasks/search/stats.
+  - `auth.go` — users, api keys, sessions.
+
+Templates live in `internal/server/templates/` and are embedded with
+`//go:embed all:templates`; shared markup is in `partial.html`
+(`header`/`footer` defines). CSS is `internal/server/static/style.css`.
+
+## Conventions
+
+- **Add a store method before a handler.** Data access belongs in
+  `internal/store/`; handlers in `internal/server/` stay thin. Use parameterized
+  queries (`?`) — never string-concatenated SQL.
+- **Error handling:** the store returns `store.ErrNotFound` (from
+  `sql.ErrNoRows`) and `store.ErrConflict` (UNIQUE violations). Handlers surface
+  these via `s.apiNotFound` (JSON) or `s.error` (HTML page). `checkAffected`
+  turns zero-rows-into-`ErrNotFound` for updates/deletes — reuse it.
+- **Validation** is done up front: trim whitespace, reject empty required
+  fields, and for the CLI enforce the min-8-char passphrase + match check.
+- **Auth:** passwords are bcrypt-hashed only (never plaintext). Session tokens
+  and api keys are stored as SHA-256 hex hashes; the raw token is shown once.
+  `checkPassword` burns comparable time for missing users to avoid an
+  enumeration timing signal.
+- **Style:** minimal, no comments unless the logic is non-obvious. HTML uses the
+  existing classes and `{{dateFmt}}` template helper; keep the Hackerman
+  terminal aesthetic.
+- **Schema changes:** extend the `migrate()` block (all tables use
+  `CREATE TABLE IF NOT EXISTS`). The pure-Go driver supports `ALTER` at runtime
+  but existing deployments only run `IF NOT EXISTS` migrations — be careful
+  adding columns to shipped tables.
+
+## When making a change
+
+1. Read the neighboring file to match its exact style and framework choices.
+2. Implement in the store first, then the handler/route.
+3. `go build -o tracker .` and `go vet ./...` — both must pass.
+4. If the change is user-facing, update the relevant README section.