chore(maestro): scaffold cargo workspace and CI

Adds the empty Cargo workspace (resolver = 2, members = crates/*),
a stable rust-toolchain pin with rustfmt + clippy, and a Gitea
Actions pipeline that runs cargo fmt --check, clippy -D warnings,
and cargo test on every push/PR.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -0,0 +1,37 @@
+name: ci
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  rust:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install stable toolchain
+        run: |
+          rustup toolchain install stable --profile minimal --component rustfmt,clippy
+          rustup default stable
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock', '**/Cargo.toml') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: fmt
+        run: cargo fmt --all -- --check
+
+      - name: clippy
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: test
+        run: cargo test --all