workflow: project-driven agent workflow (docs-first, TODO/ROADMAP tracking, verify-before-done)

- system prompt gains a Project workflow block when the repo tracks its own
  progress (TODO.md/ROADMAP.md/docs): read the task list first and keep it
  current, spec-first for non-trivial work, complete unit tests, verify before
  declaring done
- TODO.md + ROADMAP.md loaded as 'Project tracker' instruction blocks, capped
  tighter than AGENTS.md so the agent sees the shape without drowning in it
- one soft nudge per session when a turn writes files without touching the
  task list; suppressed when todo_write was called; never a gate
- /workflow command + panel showing TODO/ROADMAP/docs presence, line/file
  counts, nudge state
- config: workflow.enabled (default true), workflow.docsDir (default docs)
- prompt-cache version key extended with wf: so toggling the workflow busts
  the cached system prompt
- docs: docs/workflow.md, configuration table row, ROADMAP + TODO entries
- tests: test/workflow.test.ts (9 tests)

830 tests pass, typecheck clean, build green, live headless demo verified

docs/workflow.md

@@ -0,0 +1,83 @@
+# Project-driven agent workflow
+
+Shiro Neko treats a repository the way this project treats itself: progress
+tracked in TODO.md and ROADMAP.md, docs-driven development, spec-first plans,
+complete unit tests, and verify-before-done. When the repo keeps those files,
+the agent's system prompt carries a short workflow policy and the session
+tracks whether the workflow is being followed.
+
+## What the agent sees
+
+When the session starts in a git repo that has any of:
+
+- `TODO.md` at the git root
+- `ROADMAP.md` at the git root
+- a `docs/` directory (configurable with `workflow.docsDir`)
+
+the system prompt gains a "Project workflow" block:
+
+- read TODO.md (the task list) before starting and keep it current as you go
+- keep ROADMAP.md current when a milestone ships
+- write a short plan first (spec-first) for anything non-trivial
+- add tests alongside code; the project expects complete unit tests
+- verify with the project's check commands (tests/typecheck/build) before
+  declaring done
+
+Bare repos (no TODO, ROADMAP, or docs) get no such block — the policy only
+renders when the project itself tracks progress, so a throwaway directory does
+not collect noise.
+
+TODO.md and ROADMAP.md are also loaded into the conversation like instruction
+files (`Project tracker (...)`), capped tighter than AGENTS.md so the agent
+sees the shape of the work without filling its context. This mirrors the
+existing `AGENTS.md` / `CLAUDE.md` / `.shiro.md` loading: outermost first, git
+root down to cwd.
+
+## The nudge
+
+After a turn that wrote files (edit_file, write_file, apply_patch, ...) but
+never called `todo_write`, the session emits one soft notice:
+
+```
+reminder: you modified files without updating the project task list (TODO.md).
+Keep it current: mark what you did.
+```
+
+Design constraints:
+
+- **Once per session.** Repeating a nag trains the model to ignore it.
+- **Not a gate.** The agent stays in control; this is guidance, not a block.
+- **Only when the repo has a TODO/ROADMAP.** A repo that tracks nothing gets
+  no reminder.
+- Suppressed when the turn already called `todo_write` — the task list is
+  current, nothing to say.
+
+## Configuration
+
+```yaml
+workflow:
+  enabled: true   # master switch; default true
+  docsDir: docs   # where the project keeps developer docs; default 'docs'
+```
+
+`workflow.enabled: false` disables both the prompt policy and the nudge.
+
+## /workflow
+
+`/workflow` renders a panel with the project's tracking state and the
+session's behaviour:
+
+| row | meaning |
+|---|---|
+| `workflow` | on/off from config |
+| `TODO.md` | present? line count |
+| `ROADMAP.md` | present? line count |
+| `docs dir` | present? file count (bounded at 200) |
+| `reminders sent` | whether this session nudged (once, ever) |
+
+## Relationship to AGENTS.md
+
+AGENTS.md-style files are standing orders from the user and override the
+agent's defaults. The workflow policy is a default that documents what a
+repo tracking its own progress expects. When the two conflict, AGENTS.md
+wins — the workflow feature is a floor, not a ceiling.