fix(worktrees): the injected agent skill no longer blocks removal

With Codeman Agent Skill on (agentSkillEnabled), every session create
writes the skill into the folder the session runs in, so a session in a
worktree leaves an untracked .claude/skills/codeman/ (claude) or
.agents/skills/codeman/ (codex, gemini and the rest) behind. git then
refuses `git worktree remove` for that worktree forever, and an agent
running `git add -A` there would commit Codeman's skill into its branch
(reproduced: the worktree's status showed "?? .agents/" and
"?? .claude/").

A create now excludes <skills dir>/codeman/ next to the hooks file, for
every skills folder the registry names (capabilities.agentSkillDir,
read at call time by the route and passed in as data, so no CLI id is
branched on). Like the other lines it is only added when git does not
already ignore the path, and only to the repository's local
info/exclude.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -455,7 +455,7 @@ Further detail: the synchronous clone request is bounded by `GIT_CLONE_TIMEOUT_M
 - ⚠️ **Only `<repo>/.claude/worktrees/<valid-name>` is ever created or removed.** Every component is `lstat`ed (a symlinked `.claude`, `worktrees` or worktree folder is refused, never followed) and the real path must equal the lexical one, so a repository cannot redirect a create or remove outside itself; removal also requires git to list the folder as a worktree of THIS repository. A worktree anywhere else is listed read-only (`managed: false`). A managed worktree whose folder is GONE stays removable (`resolveManagedWorktree({ allowMissing })`, removal only, never a session start: git lists it at exactly the managed path, no component on the way is a symlink, and `git worktree remove` then only drops git's record), since otherwise its name could never be used again.
 - ⚠️ **git never runs for a case at or inside a Docker case workspace** (or whose common git dir is there), and Docker and remote cases are refused with a 400 before any git, the same rule as the git status indicator: `git worktree add` runs the repository's post-checkout hook and checkout filters ON THE HOST. That is acceptable for a local case, where the user's agent already runs code.
 - ⚠️ **Removal is `git worktree remove` WITHOUT `--force`**, refused (409) while any live session (any owner) runs at or inside the worktree, and git's own refusal (modified or untracked files, a lock) is the answer, shown through `textContent`. The optional branch delete is `git branch -d`, never `-D`: an unmerged branch survives and the response says why (`branchError`).
-- ⚠️ **The main checkout must not see the worktrees.** When `git check-ignore` says they are not ignored, `/.claude/worktrees/` is appended to the repository's LOCAL `<common git dir>/info/exclude` (never a tracked `.gitignore`), and so is `/.claude/settings.local.json`: Codeman writes its hooks there for every claude session, and an untracked copy in a worktree would make `git worktree remove` refuse forever (Claude Code covers that file with the global excludes file, which a machine may not have). A symlinked `info` dir or `exclude` file is reported, never written through.
+- ⚠️ **The main checkout must not see the worktrees.** When `git check-ignore` says they are not ignored, `/.claude/worktrees/` is appended to the repository's LOCAL `<common git dir>/info/exclude` (never a tracked `.gitignore`), and so is `/.claude/settings.local.json`: Codeman writes its hooks there for every claude session, and an untracked copy in a worktree would make `git worktree remove` refuse forever (Claude Code covers that file with the global excludes file, which a machine may not have). The agent skill copy (`<skills dir>/codeman/`, injected while `agentSkillEnabled` is on) gets a line too, for every skills folder the registry names (`capabilities.agentSkillDir`, passed in by the route as data). A symlinked `info` dir or `exclude` file is reported, never written through.
 - **Names are gated before git**: charset and length (Zod and `worktreeNameError()`), then `git check-ref-format --branch`, whose output must EQUAL the input (`--branch` expands `@{-1}`, which the charset gate already refuses). The base is a resolved commit (`rev-parse --verify <base>^{commit}`), passed after `--` with `--no-track`; an existing branch is refused (`-b`, never `-B`, which would reset it). Create and remove are serialized per repository.
 - **Sessions start through the EXISTING create paths**, never a new spawn path: `POST /api/quick-start` with `worktree` (resolved with the same guards; hooks, the agent skill, the model override and the session all target the worktree, and a case that does not exist is a 404, never a scaffold), or `POST /api/sessions` with the worktree as `workingDir` (what the Run button uses for claude and shell). The frontend launches through `run({ worktree })` with a temporary `_runMode` swap, tabs named `w<n>-<worktree>`.
 - The unified session list names a live session's worktree from its folder layout (`worktreeFromPath`), so a codex or shell session gets the worktree pill before (or without) a transcript record.