docs: add human-facing pages for the remaining 22 promoted skills

Adds a docs page for every promoted skill that lacked one, following
.agents/writing-docs.md and using docs/engineering/to-prd.md as the
worked exemplar. Covers all of engineering/ (bar to-prd, already done),
productivity/, and misc/.

Each page states its load-bearing constraint, its invocation mode and
trigger boundary, surfaces the skill's leading word, and routes back to
ask-matt so the set forms a connected router with no dead ends.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/misc/git-guardrails-claude-code.md

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+Quickstart:
+
+```bash
+npx skills add mattpocock/skills --skill=git-guardrails-claude-code
+```
+
+```bash
+npx skills update git-guardrails-claude-code
+```
+
+[Source](https://github.com/mattpocock/skills/tree/main/skills/misc/git-guardrails-claude-code)
+
+## What it does
+
+`git-guardrails-claude-code` installs a Claude Code **PreToolUse hook** that blocks destructive git commands — `git push`, `reset --hard`, `clean -f`, `branch -D`, `checkout .` / `restore .` — before they run.
+
+The load-bearing constraint: this is a **guardrail**, not a request. The block lives in the harness, not in the agent's instructions — the hook inspects every Bash command and, on a match, exits with code 2 so the command never executes. An agent can forget a "please don't push" note in its prompt; it cannot talk its way past a hook that fires before the tool call lands.
+
+## When to reach for it
+
+Type `/git-guardrails-claude-code`, or the agent reaches for it automatically when a task fits.
+
+Reach for it when you want an agent to work freely in a repo but never perform the handful of git operations that lose work or rewrite shared history. It's a one-time install: run it once per project (or once globally) and the guardrail is standing thereafter. For enforcing quality *at commit time* — Prettier, type-checking, tests via Husky — that's a different mechanism, so use [setup-pre-commit](https://aihero.dev/skills-setup-pre-commit) instead.
+
+## The guardrail
+
+The hook is a small shell script matching each Bash command against a list of dangerous patterns. When one matches, the agent sees a `BLOCKED` message telling it that it does not have authority to run that command, and the command is dropped.
+
+Two knobs at install time: **scope** — this project (`.claude/settings.json`) or all projects (`~/.claude/settings.json`) — and the **pattern list**, which you can extend or trim so the wall sits exactly where you want it. Everything not on the list still runs untouched.
+
+## It's working if
+
+- A blocked command (e.g. `git push`) never executes, and the agent reports it was denied rather than that it failed.
+- Ordinary git — `add`, `commit`, `status`, `checkout <branch>` — runs as normal.
+
+## Where it fits
+
+This is a **run-once setup** skill, and a standalone: install the guardrail and forget it. Its closest neighbour is [setup-pre-commit](https://aihero.dev/skills-setup-pre-commit), which also writes hooks into a repo but guards commit *quality* rather than destructive git *actions* — the two stack cleanly. When you're unsure which safety or setup skill fits, [ask-matt](https://aihero.dev/skills-ask-matt) routes you.