feat(hooks): add global hooks — PreCompact priorities + git/gh confirm modals

Three new machine-wide hooks installed via `make install-hooks`:

- `precompact-priorities.sh` (PreCompact) — injects a priority block into
  the compaction prompt so the generated summary retains information most
  expensive to reconstruct: unanswered questions, root causes with
  file:line, subagent findings as primary evidence, exact numbers/IDs,
  A-vs-B decisions, open TODOs, classified-data handling.

- `git-commit-confirm.py` (PreToolUse/Bash) — gates `git commit` behind a
  confirmation modal showing parsed message, staged files, diff stats,
  author. Parses both HEREDOC and `-m`/`--message` forms.

- `gh-pr-create-confirm.py` (PreToolUse/Bash) — gates `gh pr create`
  behind a modal showing title, base ← head, reviewers, labels,
  assignees, milestone, draft flag, body (HEREDOC or quoted).

Makefile: adds `install-hooks` / `uninstall-hooks` targets and extends
`list` with a Hooks section. Install prints the settings.json snippet
(in `hooks/settings-snippet.json`) to merge into `~/.claude/settings.json`.

Also: `languages/elisp/claude/hooks/validate-el.sh` now emits JSON with
`hookSpecificOutput.additionalContext` on failure (via new `fail_json()`
helper) so Claude sees a structured error in context, in addition to
the existing stderr output and exit 2.

Patterns synthesized clean-room from fcakyon/claude-codex-settings
(Apache-2.0). Each hook is original content.

1 files changed, 113 insertions, 0 deletions

diff --git a/hooks/README.md b/hooks/README.md
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+# Global Hooks
+
+Machine-wide Claude Code hooks that install into `~/.claude/hooks/` and apply to every project on this machine. These complement the per-project hooks installed by language bundles (e.g., `languages/elisp/claude/hooks/validate-el.sh`).
+
+## What's here
+
+| Hook | Trigger | Purpose |
+|---|---|---|
+| `precompact-priorities.sh` | `PreCompact` | Injects a priority-preservation block into Claude's compaction prompt so the generated summary retains information most expensive to reconstruct (unanswered questions, root causes with `file:line`, subagent findings, exact numbers/IDs, A-vs-B decisions, open TODOs, classified-data handling). |
+| `git-commit-confirm.py` | `PreToolUse(Bash)` | Gates `git commit` behind a confirmation modal showing the parsed message, staged files, diff stats, and git author. Parses both HEREDOC and `-m`/`--message` forms. |
+| `gh-pr-create-confirm.py` | `PreToolUse(Bash)` | Gates `gh pr create` behind a confirmation modal showing title, base←head, reviewers, labels, assignees, milestone, draft flag, and body (HEREDOC or quoted). |
+
+## Install
+
+### One-liner (from this repo)
+
+```bash
+make -C ~/code/rulesets install-hooks
+```
+
+That symlinks each hook into `~/.claude/hooks/` and prints the `settings.json` snippet you need to merge into `~/.claude/settings.json` to wire them up.
+
+### Manual install
+
+```bash
+mkdir -p ~/.claude/hooks
+ln -sf ~/code/rulesets/hooks/precompact-priorities.sh ~/.claude/hooks/precompact-priorities.sh
+ln -sf ~/code/rulesets/hooks/git-commit-confirm.py   ~/.claude/hooks/git-commit-confirm.py
+ln -sf ~/code/rulesets/hooks/gh-pr-create-confirm.py ~/.claude/hooks/gh-pr-create-confirm.py
+```
+
+Then merge into `~/.claude/settings.json`:
+
+```json
+{
+  "hooks": {
+    "PreCompact": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "~/.claude/hooks/precompact-priorities.sh"
+          }
+        ]
+      }
+    ],
+    "PreToolUse": [
+      {
+        "matcher": "Bash",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "~/.claude/hooks/git-commit-confirm.py"
+          },
+          {
+            "type": "command",
+            "command": "~/.claude/hooks/gh-pr-create-confirm.py"
+          }
+        ]
+      }
+    ]
+  }
+}
+```
+
+Note: if `~/.claude/settings.json` already has `hooks` entries, merge arrays rather than replacing them. Both `git-commit-confirm.py` and `gh-pr-create-confirm.py` are safe to run on every `Bash` tool call — they no-op on anything that isn't their target command.
+
+## Verify
+
+After installing + reloading Claude Code (or using `/hooks` to reload):
+
+```bash
+# Test git commit gating
+echo '{"tool_name":"Bash","tool_input":{"command":"git commit -m \"test\""}}' \
+  | ~/.claude/hooks/git-commit-confirm.py
+
+# Test gh pr create gating
+echo '{"tool_name":"Bash","tool_input":{"command":"gh pr create --title test --body body"}}' \
+  | ~/.claude/hooks/gh-pr-create-confirm.py
+
+# Test precompact block (just prints the rules)
+~/.claude/hooks/precompact-priorities.sh | head -20
+```
+
+Each should produce JSON output (the first two) or markdown (the third).
+
+## Per-project vs global
+
+These three live in `~/.claude/hooks/` because they're editor-agnostic and language-agnostic — you want them firing on every project. Per-language hooks (like `validate-el.sh` for Elisp or future equivalents for Python / TypeScript / Go) live in `languages/<lang>/claude/hooks/` and install *per-project* via `make install-<lang> PROJECT=<path>`.
+
+## Hook output contract
+
+The Python hooks emit JSON to stdout with `hookSpecificOutput`:
+
+- `hookEventName: "PreToolUse"`
+- `permissionDecision: "ask"`
+- `permissionDecisionReason: "<formatted modal text>"`
+
+Claude Code reads that and surfaces the modal to the user before running the tool. If the user declines, the tool call is cancelled. If they accept, it proceeds normally.
+
+The PreCompact hook emits markdown prose to stdout, which Claude Code appends to the default compaction prompt before generating the summary.
+
+## Dependencies
+
+- `python3` — for the two Python hooks (any modern version; stdlib only)
+- `bash` — for `precompact-priorities.sh`
+- `git` — the commit hook queries `git diff --cached` and `git config user.name` / `user.email`
+- No external Python packages required
+
+## Sources
+
+- PreCompact priority-preservation pattern + git/gh confirmation modal pattern: clean-room synthesis from fcakyon's `claude-codex-settings` (Apache-2.0), extended and adapted. See `docs/architecture/v2-todo.org` or skill-evaluation memory for context.
+- Each hook is original content; patterns are ideas, not copied prose.