refactor(git-worktrees): retrofit to the ADR-0020 context contract

Description 592 -> 248 chars, body 756 -> 515 words, Gotchas 8 -> 4.

The audit found the dispatch table had no row for a worktree on an
existing local branch, so that request fell to the adjacent -B row, which
resets the branch to HEAD and discards its commits. Non-destructive create
is now the first row and -B names its own destructiveness. Adds the missing
lock/unlock row and repair's run-from constraint.

plugins/git/.apm/skills/git-worktrees/references/worktrees.md

@@ -4,6 +4,27 @@ source_keys:
   - git-scm-worktree-docs
 ---
 
+## Shared vs. per-worktree state
+
+All worktrees share one object store, one config, and most refs under `refs/`. Each worktree keeps
+its own `HEAD`, index, and per-worktree metadata (`ORIG_HEAD`, `MERGE_HEAD`, `refs/bisect/`,
+`refs/worktree/`, `refs/rewritten/`) under `$GIT_DIR/worktrees/<name>/`. Exactly one **main
+worktree** exists per repo — the one `git init` or `git clone` produced — and it cannot be removed
+or moved. Every other worktree is a **linked worktree** created by `git worktree add`.
+
+## `add` forms
+
+```bash
+git worktree add <path> <branch>              # check out an existing branch — non-destructive
+git worktree add -b <branch> <path>           # create a new branch; fails if it exists
+git worktree add <path>                       # branch named after $(basename <path>): checked out
+                                              # if it exists, else created from HEAD
+git worktree add -B <branch> <path>           # create the branch, or reset an existing one to HEAD,
+                                              # discarding the commits it carried
+git worktree add <path> <remote>/<branch>     # track a remote branch
+git worktree add -d <path>                    # detached HEAD, no branch
+```
+
 ## Full `add` flag table
 
 | Flag | Meaning |
@@ -52,6 +73,16 @@ git worktree add <path> <remote>/<branch>
 ```
 For ambiguous names across remotes, `checkout.defaultRemote` config disambiguates explicitly, or `--guess-remote` auto-matches by path basename (default controlled by `worktree.guessRemote` config). If a branch name matches multiple remotes during `worktree add` and neither is set, Git refuses rather than guessing.
 
+## Repair after a manual move
+
+```bash
+git worktree repair            # run from the main worktree: fixes the links to every linked worktree
+git worktree repair <path>     # run from a moved linked worktree: fixes its own pointer back to main
+```
+
+`repair` reestablishes the bidirectional pointers a manual move breaks, but only for the side it is
+run from. Run it from the wrong directory and it reports nothing and fixes nothing.
+
 ## Configuration
 
 | Key | Effect |
@@ -61,3 +92,25 @@ For ambiguous names across remotes, `checkout.defaultRemote` config disambiguate
 | `gc.worktreePruneExpire` | How long before stale worktree metadata is pruned by `git gc` |
 | `extensions.worktreeConfig` | Enable per-worktree config scope (`config.worktree` file) — see Gotchas in SKILL.md |
 | `checkout.defaultRemote` | Disambiguates which remote to use when a branch name matches multiple remotes during `worktree add` |
+
+## Workflow patterns
+
+**Emergency fix without disrupting current work** — nothing is stashed, and the main worktree is
+untouched throughout:
+
+```bash
+git worktree add -b emergency-fix ../temp main
+cd ../temp
+# fix, then commit
+git commit -a -m "fix: critical production bug"
+cd -
+git worktree remove ../temp
+```
+
+**Review a PR branch alongside your own work** — both branches stay checked out, so there is no
+context switch:
+
+```bash
+git worktree add ../review-pr-123 origin/feature-xyz
+# open ../review-pr-123 in a second editor window or terminal
+```