fix(git): correct three command claims the plugin got wrong, and give rebase an owner

Three statements were false against the git in use (2.39.5), each verified by
running it.

`git rebase --autosquash HEAD~N` without `-i` is a silent no-op: git prints
"Successfully rebased", the `fixup!` commit survives with the same SHA, and
rewrite-history.md presented that as the preferred flow with `-i` as an optional
review step. The agent reports the squash as done and the `fixup!` subject then
trips this repo's own commit-msg gate. `-i` is now the command, not the alternative.

"Fetch never modifies a local branch, so it is always safe to run" — new text on
this branch — is false: `git fetch origin main:probe` fast-forwarded the local
branch, and a `+` prefix force-updates it, losing commits. The claim is scoped to
the no-refspec form.

`git worktree add --orphan` does not exist before Git 2.42; on 2.39.5 it is
`error: unknown option 'orphan'`, exit 129. The same file gives a version floor for
`--recurse-submodules` three sections earlier. Floor added, with a fallback that
was tested before being documented.

git-workflow claimed "every request resolves to exactly one of these six" while
rebase, reset and stash were owned by no skill — `git reset` appeared nowhere in
the plugin, old tree or new — so "undo my last commit" routed nowhere. The claim is
gone, the router gains rows for all three, and the procedures now exist: plain
rebase with `--onto` and conflict handling, a reset mode table gated on `--hard`,
and stash save/pop/list/drop. `--hard` gets an always-loaded Gotcha, matching the
register the force-push refusal already sets.

Cherry-pick had three claimants pointing at git-history while git-commits owned the
flow, and the two copies were not equivalent — git-history's lacked the destination
check, the rtk prefix and `--abort`. Resolved to git-commits per #112; the weaker
duplicate is replaced by a hand-off.

git-commits' metadata.version was deleted rather than bumped in 14af50b, leaving two
house-contract documents citing a worked v0.1.2 to v0.1.3 transition against a file
declaring no version. Restored to 0.1.3.

Also: the divergent-pull explanation stated a `--ff-only` default that does not
exist (it is a hard error); `--remote` "requires" a configured branch where it uses
one; `git push origin --delete` moved to git-remotes, which owns the remote-side
gates; seven retired `git:<name>` source slugs; git-orchestrate quoted a
git-workflow sentence that no longer exists; git-submodules regains the indirect
trigger that made "add a dependency repo" routable; and commit atomicity is a common
gate rather than reachable only from the create flow.

Refs: #112, #113

plugins/git/skills/git-branches/SKILL.md

@@ -33,7 +33,7 @@ The two patterns are not mixable, and the wrong merge rule silently damages hist
 
 | Action | Reference |
 |---|---|
-| create, switch, delete, rename, track, list, get-intent | `references/branch-operations.md` |
+| create, switch, delete, rename, track, list, get-intent, stash | `references/branch-operations.md` |
 | merge a branch, resolve merge conflicts | `references/merging.md` |
 | compare two branches, find their divergence | `references/comparing-branches.md` |
 
@@ -51,7 +51,7 @@ These gates are passable. The `main`/`master` refusal in Gotchas is not.
 
 ## Step 4 — Set tracking
 
-When pushing a branch for the first time, always `git push -u origin <branch>`. Without an upstream, later pushes and pulls either fail or silently target the wrong remote branch, and the caller has no way to tell which happened.
+A new branch's first push must be `git push -u origin <branch>`. The push itself is `git-remotes`' — every remote-side gate lives there, which is why Step 2's remote-delete row hands off the same way — but the upstream requirement originates here, so carry it in the handoff. Without an upstream, later pushes and pulls either fail or silently target the wrong remote branch, and the caller has no way to tell which happened.
 
 ## Step 5 — Return a structured result