chore(git-workflow): add 3-repo feature branch skills + helper scripts

.claude/skills/git-feature-sync/SKILL.md

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+---
+name: git-feature-sync
+description: Rebase the current feature branch onto main in all 3 repos (root + kicad + wxwidgets). Naturally re-runnable - after the user resolves a conflict manually and runs `git rebase --continue`, re-invoke the skill and it picks up where it stopped. Usage - "/git-feature-sync".
+---
+
+# git-feature-sync
+
+Rebase the current feature branch onto each repo's main, across root, kicad, and wxwidgets.
+
+Per-repo main mapping is in `scripts/git-workflow/repos.sh` (root=`main`, subs=`wasm-port`).
+
+## How "resume after conflict" works
+
+There is **no state file**. State is derived live each run:
+- `git -C <p> merge-base --is-ancestor origin/<main> HEAD` → if 0, the branch already contains the latest main; skip this repo.
+- `.git/rebase-merge` or `.git/rebase-apply` directory present → rebase is mid-flight in that repo; refuse to do anything until the user finishes or aborts it.
+
+So after the user resolves a conflict manually + runs `git rebase --continue` in the stopped repo, just re-running `/git-feature-sync` picks up at the next un-rebased repo.
+
+## Steps
+
+1. **Get status snapshot.** Run `bash /Users/torcsi/dev/kicad-wasm/scripts/git-workflow/repo-status.sh` and parse the per-repo JSON.
+
+2. **Pre-flight checks.**
+   - If any repo has `rebase_in_progress: true`, STOP. Tell the user which repo, and that they need to resolve (`git -C <repo> rebase --continue` after `git add`-ing resolved files) or abort (`git -C <repo> rebase --abort`) before sync can proceed.
+   - Determine the feature branch from root's `branch` field. If root is on its main (`main`) or detached, STOP and say "no feature branch active in root — nothing to sync".
+   - For each submodule with `branch != <feature-branch>`:
+     - If branch is empty (detached), prose-ask: "wxwidgets is at detached HEAD `<sha>`. Want me to `git -C wxwidgets checkout <feature-branch>` first? (y/N)". On yes, run it (auto-allowed). On no, STOP.
+     - If branch is some other name, STOP and tell the user which repo is on which branch. Don't auto-switch.
+
+3. **Determine work plan.** For each repo, mark "needs rebase" if `up_to_date_with_main: false`. If all three are up-to-date, print "all 3 repos already up to date with their mains" and stop cleanly.
+
+4. **Execute per repo** in order [root, kicad, wxwidgets]. Skip any repo with `up_to_date_with_main: true`. For each repo that needs rebase:
+   - Prose-announce: "About to rebase <repo> (`<feature>`) onto `origin/<main>` — proceed?"
+   - `git -C <path> fetch origin`
+   - `git -C <path> rebase origin/<main>` (this hits the `ask` permission — user confirms again at tool layer)
+   - If the rebase command exits non-zero (conflict), STOP and emit the handoff message (see below).
+   - On success, continue to the next repo.
+
+5. **After all 3 succeed:** check `git -C <root> status --short` for staged or unstaged changes to the `kicad` / `wxwidgets` submodule entries. If present, suggest:
+   > Submodule SHAs changed during rebase. When ready: `/git-feature-commit "sync: bump submodule pointers after rebase"`.
+   Do NOT auto-commit.
+
+## Conflict handoff message — use this exact shape
+
+When a rebase fails mid-flight in repo X, list the repos in the plan, what's been done, what's pending, and the manual commands to resolve. Derive everything live by re-running `repo-status.sh` if needed.
+
+> **Completed:** root rebased onto origin/main (3 commits replayed).
+> **Stopped:** kicad — conflict during rebase. Conflicted files:
+> ```
+> kicad/eeschema/foo.cpp
+> kicad/common/bar.cpp
+> ```
+> **Pending:** wxwidgets (not started).
+>
+> **To resolve manually:**
+> ```
+> cd /Users/torcsi/dev/kicad-wasm/kicad
+> # edit each conflicted file, resolve <<<<<<< markers
+> git add eeschema/foo.cpp common/bar.cpp
+> git rebase --continue
+> ```
+>
+> Then re-run `/git-feature-sync` — kicad will be detected as already rebased and it will proceed with wxwidgets.
+>
+> To roll back kicad only: `cd /Users/torcsi/dev/kicad-wasm/kicad && git rebase --abort`. Note: already-rebased repos (root in this case) **stay rebased** — they are not rolled back.
+
+Get the conflicted-files list from `git -C <path> diff --name-only --diff-filter=U`.
+
+## Safety
+
+- Never `--force` anything.
+- Never `git rebase --skip` on the user's behalf — only `--continue` is safe and that's the user's job after manual resolution.
+- Always echo the command before running it.
+- Detached HEAD in a submodule is a confirmation point, never an auto-fix.