feat: Add skill discovery, loading, and invocation (#3444)

Adds a skills system that lets users define reusable LLM instructions as `SKILL.md` files with YAML frontmatter.

1 files changed, 154 insertions, 0 deletions

diff --git a/.claude/skills/hunk/SKILL.md b/.claude/skills/hunk/SKILL.md
new file mode 100644
index 00000000..2306293f
--- /dev/null
+++ b/.claude/skills/hunk/SKILL.md
@@ -0,0 +1,154 @@
+---
+name: hunk-review
+description: Interacts with live Hunk diff review sessions via CLI. Inspects review focus, navigates files and hunks, reloads session contents, and adds inline review comments. Use when the user has a Hunk session running or wants to review diffs interactively.
+---
+
+# Hunk Review
+
+Hunk is an interactive terminal diff viewer. The TUI is for the user -- do NOT run `hunk diff`, `hunk show`, or other interactive commands directly. Use `hunk session *` CLI commands to inspect and control live sessions through the local daemon.
+
+If no session exists, ask the user to launch Hunk in their terminal first.
+
+## Workflow
+
+```text
+1. hunk session list                                    # find live sessions
+2. hunk session get --repo .                            # inspect path / repo / source
+3. hunk session review --repo . --json                  # inspect file/hunk structure first
+4. hunk session review --repo . --include-patch --json  # opt into raw diff text only when needed
+5. hunk session context --repo .                        # check current focus when needed
+6. hunk session navigate ...                            # move to the right place
+7. hunk session reload -- <command>                     # swap contents if needed
+8. hunk session comment add ...                         # leave one review note
+9. hunk session comment apply ...                       # apply many agent notes in one stdin batch
+```
+
+## Session selection
+
+Most session commands accept:
+
+- `--repo <path>` -- match the live session by its current loaded repo root (most common)
+- `<session-id>` -- match by exact ID (use when multiple sessions share a repo)
+- If only one session exists, it auto-resolves
+
+`reload` also supports:
+
+- `--session-path <path>` -- match the live Hunk window by its current working directory
+- `--source <path>` -- load the replacement `diff` / `show` command from a different directory
+
+Use `--source` only for advanced reloads where the live session you want to control is not already associated with the checkout you want to load next. For a normal worktree session, prefer selecting it directly with `--repo /path/to/worktree`.
+
+## Commands
+
+### Inspect
+
+```bash
+hunk session list [--json]
+hunk session get (--repo . | <id>) [--json]
+hunk session context (--repo . | <id>) [--json]
+hunk session review (--repo . | <id>) [--json] [--include-patch]
+```
+
+- `get` shows the session `Path`, `Repo`, and `Source`, which helps when choosing between `--repo` and `--session-path`
+- `Repo` is what `--repo` matches; `Path` is what `--session-path` matches
+- `review --json` returns file and hunk structure by default; add `--include-patch` only when a caller truly needs raw unified diff text
+
+### Navigate
+
+Absolute navigation requires `--file` and exactly one of `--hunk`, `--new-line`, or `--old-line`:
+
+```bash
+hunk session navigate --repo . --file src/App.tsx --hunk 2
+hunk session navigate --repo . --file src/App.tsx --new-line 372
+hunk session navigate --repo . --file src/App.tsx --old-line 355
+```
+
+Relative comment navigation jumps between annotated hunks and does not require `--file`:
+
+```bash
+hunk session navigate --repo . --next-comment
+hunk session navigate --repo . --prev-comment
+```
+
+- `--hunk <n>` is 1-based
+- `--new-line` / `--old-line` are 1-based line numbers on that diff side
+- Use either `--next-comment` or `--prev-comment`, not both
+
+### Reload
+
+Swaps the live session's contents. Pass a Hunk review command after `--`:
+
+```bash
+hunk session reload --repo . -- diff
+hunk session reload --repo . -- diff main...feature -- src/ui
+hunk session reload --repo . -- show HEAD~1
+hunk session reload --repo . -- show HEAD~1 -- README.md
+hunk session reload --repo /path/to/worktree -- diff
+hunk session reload --session-path /path/to/live-window --source /path/to/other-checkout -- diff
+```
+
+- Always include `--` before the nested Hunk command
+- `--repo` or `<session-id>` usually selects the session you want
+- `--source` is advanced: it does not select the session; it only changes where the replacement review command runs
+- If the live session is already showing the target worktree, prefer `hunk session reload --repo /path/to/worktree -- diff`
+- `--session-path` targets the live window when you need to keep session selection separate from reload source
+
+### Comments
+
+```bash
+hunk session comment add --repo . --file README.md --new-line 103 --summary "Tighten this wording" [--rationale "..."] [--author "agent"] [--focus]
+printf '%s\n' '{"comments":[{"filePath":"README.md","newLine":103,"summary":"Tighten this wording"}]}' | hunk session comment apply --repo . --stdin [--focus]
+hunk session comment list --repo . [--file README.md]
+hunk session comment rm --repo . <comment-id>
+hunk session comment clear --repo . --yes [--file README.md]
+```
+
+- `comment add` is best for one note; `comment apply` is best when an agent already has several notes ready
+- `comment add` requires `--file`, `--summary`, and exactly one of `--old-line` or `--new-line`
+- `comment apply` payload items require `filePath`, `summary`, and exactly one target such as `hunk`, `hunkNumber`, `oldLine`, or `newLine`
+- `comment apply` reads a JSON batch from stdin and validates the full batch before mutating the live session
+- Pass `--focus` when you want to jump to the new note or the first note in a batch
+- `comment list` and `comment clear` accept optional `--file`
+- Quote `--summary` and `--rationale` defensively in the shell
+
+## New files in working-tree reviews
+
+`hunk diff` includes untracked files by default. If the user wants tracked changes only, reload with `--exclude-untracked`:
+
+```bash
+hunk session reload --repo . -- diff --exclude-untracked
+```
+
+## Guiding a review
+
+The user may ask you to walk them through a changeset or review code using Hunk. Start with `hunk session review --json` to understand the file/hunk structure without inflating agent context, then use `--include-patch` only for the files you truly need to read in raw diff form. Use `context` and `navigate` to line up the user's current view before adding comments.
+
+Your role is to narrate: steer the user's view to what matters and leave comments that explain what they're looking at.
+
+Typical flow:
+
+1. Load the right content (`reload` if needed)
+2. Navigate to the first interesting file / hunk
+3. Add a comment explaining what's happening and why
+4. If you already have several notes ready, prefer one `comment apply` batch over many separate shell invocations
+5. Summarize when done
+
+Guidelines:
+
+- Work in the order that tells the clearest story, not necessarily file order
+- Navigate before commenting so the user sees the code you're discussing
+- Use `comment apply` for agent-generated batches and `comment add` for one-off notes
+- Use `--focus` sparingly when the note itself should actively steer the review
+- Keep comments focused: intent, structure, risks, or follow-ups
+- Don't comment on every hunk -- highlight what the user wouldn't spot themselves
+
+## Common errors
+
+- **"No visible diff file matches ..."** -- the file is not in the loaded review. Check `context`, then `reload` if needed.
+- **"No active Hunk sessions"** -- ask the user to open Hunk in their terminal.
+- **"Multiple active sessions match"** -- pass `<session-id>` explicitly.
+- **"No active Hunk session matches session path ..."** -- for advanced split-path reloads, verify the live window `Path` via `hunk session get` or `list`, then use `--session-path`.
+- **"Pass the replacement Hunk command after `--`"** -- include `--` before the nested `diff` / `show` command.
+- **"Pass --stdin to read batch comments from stdin JSON."** -- `comment apply` only reads its batch payload from stdin.
+- **"Specify exactly one navigation target"** -- pick one of `--hunk`, `--old-line`, or `--new-line`.
+- **"Specify either --next-comment or --prev-comment, not both."** -- choose one comment-navigation direction.