session: pickup and wrap around the task flow, one disposable handoff (V-445)

task start and task pr already own the branch, the identity and the PR.
What was missing sat on either side of them.

pickup runs task start, reads TASK.md and any handoff, then restates the
assumption set and stops. That pause is the point: every wasted session
here began with an agent that inferred the goal instead of stating it
back. wrap runs the tests, updates the durable docs, commits in slices,
calls task pr, and records in Vikunja what task pr cannot know.

HANDOFF.md is gitignored and injected by a SessionStart hook. It holds
what the next agent needs to resume and nothing else. TASK.md is the
brief for the branch and does not change. Anything that would still
matter next week goes to Vikunja, CLAUDE.md or docs/.

CLAUDE.md documented none of this, which is why an agent would rebuild
it. It does now, including the two hooks in ~/.claude/hooks.

.claude/ was ignored wholesale. The workflow is now tracked, because how
a session behaves should be reviewed like code.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CLAUDE.md

@@ -213,3 +213,60 @@ data pans on a phone. Local preview + headless screenshot recipe is in `AGENTS.m
 
 This repo is project **Maven** (ID 2) in Vikunja. MCP: `http://localhost:9100/mcp` (or
 `http://192.168.1.104:9100/mcp` from workpc). Feature/bug/deploy tasks go there.
+
+Vikunja is the durable task store. A task holds the goal, the constraints and the
+assumption ledger. Work without a task id is work nobody can resume, so a session that
+has no id asks for one before it starts.
+
+## Session workflow
+
+`~/.local/bin/task` owns the branch, the commit identity and the PR. One task, one
+session, one PR.
+
+```sh
+task start <vikunja-id>   # branch off origin/master, write TASK.md, fetch review comments
+task pr                   # push, open or refresh the PR, label Vikunja, notify
+task comments             # re-pull this branch's review comments into .task/
+```
+
+Around that, `/pickup` opens a session and `/wrap` closes it. Wrap at roughly half
+context rather than letting the session compact.
+
+Five stores, and each one owns something the others must not hold:
+
+| Store | Holds | Lifetime |
+|---|---|---|
+| Vikunja task | goal, constraints, assumption ledger, status | durable |
+| `CLAUDE.md`, `AGENTS.md` | what an agent must know before touching code | durable |
+| `docs/` | design, measurements, decisions | durable |
+| `TASK.md` | the brief for this branch, written by `task start`, immutable | one branch |
+| `HANDOFF.md` | only what the next agent needs to resume | one session |
+
+`TASK.md` and `.task/` are excluded through `.git/info/exclude`. `HANDOFF.md` is
+gitignored and injected at session start. If a line in the handoff would still matter
+next week, it is in the wrong file.
+
+Docs are tiered by path, so staleness is visible from the filename. Files directly under
+`docs/` are living and carry a `Last verified: <date> @ <sha>` line. Files under
+`docs/evals/` are dated measurements and are never edited after the day, so a newer
+number is a new file. Files under `docs/archive/` are dead and read by nobody by default.
+
+## Git guards
+
+Two hooks in `.githooks/`, tracked, wired with `core.hooksPath`. Fresh clone:
+
+```sh
+git config core.hooksPath .githooks
+```
+
+- `pre-commit` refuses master, and refuses more than 300 changed lines in non-markdown
+  files. Markdown is exempt and may land as one batch.
+- `commit-msg` requires the subject to end with `(V-<id>)`. `V-` and not `#`, because
+  Gitea autolinks `#123` to a Gitea issue, which is the wrong tracker.
+
+Two more guards live outside the repo, in `~/.claude/hooks/`. `diff-budget.sh` blocks
+further edits past 600 changed lines on a `task/` branch. `prose_lint_hook.py` checks
+prose on every write. Both measure against `origin/master`, so a local master that is
+ahead of the remote makes the diff budget read high.
+
+`--no-verify` exists. Using it means saying why in the commit body.