ci(maestro): fix runner image + trigger on linear/** branches

CI has been red since NAP-211 because docker.gitea.com/runner-images:
ubuntu-latest has no `rustup`; the toolchain install step exits 127.

- Use `rust:1.83-bookworm` as the job container so rustup + cargo + a
  stable toolchain are pre-installed
- Install `tmux` + `git` so the daemon integration tests can run
- Add `rustfmt` and `clippy` components
- Also trigger on pushes to `linear/**` so yolo branches see CI before
  they're merged

.gitea/workflows/ci.yml

@@ -2,19 +2,26 @@ name: ci
 
 on:
   push:
-    branches: [main]
+    branches:
+      - main
+      - 'linear/**'
   pull_request:
 
 jobs:
   rust:
     runs-on: ubuntu-latest
+    container:
+      image: rust:1.83-bookworm
     steps:
       - uses: actions/checkout@v4
 
-      - name: Install stable toolchain
+      - name: Install runtime test deps (tmux + git)
         run: |
-          rustup toolchain install stable --profile minimal --component rustfmt,clippy
-          rustup default stable
+          apt-get update
+          apt-get install -y --no-install-recommends tmux git ca-certificates
+
+      - name: Add rustfmt + clippy
+        run: rustup component add rustfmt clippy
 
       - name: Cache cargo
         uses: actions/cache@v4