ci: scope native/wheel/dashboard jobs to relevant paths (unstarve the queue) (#2155)

## Problem
CI's `changes` paths-filter is too coarse: both `code` and `e2e` include
the catch-all `headroom/**`, so **any** Python change fires the full
matrix — including the scarce-runner hogs: `build-wheel-windows`,
`macos-native-wrapper`, `windows-native-wrapper`, `docker-native-e2e`.
macOS runners cap at 5 on the Free plan, so a trivial Python PR burns
the scarcest resource. `init-e2e`/`wrap-e2e` trigger on `headroom/**`
too.

## Change (CI config only — no product code)
- **ci.yml:** split `changes` into `code` / `native` / `dashboard` /
`packaging`. Re-gate:
  | job | before | after |
  |-----|--------|-------|
  | `build-wheel-windows` | code | `packaging` |
  | `test-dashboard-ui` | code | `dashboard` |
  | `docker-native-e2e` | e2e | `native` |
  | `windows-native-wrapper` | e2e | `native` |
  | `macos-native-wrapper` | e2e | `native` |
- **init-e2e / wrap-e2e:** scoped off `headroom/**` onto the
`cli`/`install`/`providers`/`rtk` subpaths the flows exercise (mirrors
the existing `*-native-e2e` workflows).

## Safety
- Verified no job `needs:` any of the re-gated jobs, so no dependency
chain breaks. `test-dashboard-ui` still gets `build-wheel` (dashboard
files are under `headroom/` ⟹ `code` too).
- Job-level `if:` skips resolve as **neutral** (not failing), so this is
safe even if branch protection is added.
- Full matrix still runs on any `.github/workflows/**` change and on
push to `main` (post-merge safety net).

## Net
A pure-Python logic PR skips ~7-9 jobs incl. all 3 native platform
builds — freeing the macOS/Windows caps that were starving the queue.

.github/workflows/ci.yml

@@ -43,7 +43,9 @@ jobs:
     timeout-minutes: 5
     outputs:
       code: ${{ steps.filter.outputs.code }}
-      e2e: ${{ steps.filter.outputs.e2e }}
+      native: ${{ steps.filter.outputs.native }}
+      dashboard: ${{ steps.filter.outputs.dashboard }}
+      packaging: ${{ steps.filter.outputs.packaging }}
       workflows: ${{ steps.filter.outputs.workflows }}
     steps:
       - uses: actions/checkout@v7
@@ -61,14 +63,41 @@ jobs:
               - 'tests/**'
               - 'scripts/**'
               - '.github/workflows/**'
-            e2e:
-              - 'headroom/**'
+            # native = anything that can change the compiled wrapper, the native
+            # install flow, or the docker image (drives the scarce macOS/Windows
+            # runners + docker E2E). A pure-Python logic change hits none of these.
+            native:
+              - 'headroom/cli/**'
+              - 'headroom/install/**'
+              - 'headroom/providers/**'
+              - 'headroom/rtk/**'
               - 'crates/**'
+              - '**/*.rs'
+              - 'Cargo.toml'
+              - 'Cargo.lock'
+              - 'rust-toolchain.toml'
               - 'docker/**'
               - 'Dockerfile'
               - 'e2e/**'
               - 'scripts/install*'
               - 'pyproject.toml'
+              - '.github/workflows/**'
+            dashboard:
+              - 'headroom/dashboard/**'
+              - '.github/workflows/**'
+            # packaging = anything that changes how the wheel is built (so the
+            # cross-platform wheel build only reruns when the build actually changes).
+            packaging:
+              - 'pyproject.toml'
+              - 'Cargo.toml'
+              - 'Cargo.lock'
+              - 'uv.lock'
+              - 'rust-toolchain.toml'
+              - 'crates/**'
+              - '**/*.rs'
+              - 'scripts/**'
+              - 'MANIFEST.in'
+              - '.github/workflows/**'
             workflows:
               - '.github/workflows/**'
 
@@ -122,7 +151,7 @@ jobs:
 
   build-wheel-windows:
     needs: changes
-    if: needs.changes.outputs.code == 'true'
+    if: needs.changes.outputs.packaging == 'true'
     runs-on: windows-latest
     timeout-minutes: 45
     steps:
@@ -354,7 +383,7 @@ jobs:
 
   test-dashboard-ui:
     needs: [changes, build-wheel]
-    if: needs.changes.outputs.code == 'true'
+    if: needs.changes.outputs.dashboard == 'true'
     runs-on: ubuntu-latest
     timeout-minutes: 20
     steps:
@@ -474,7 +503,7 @@ jobs:
 
   docker-native-e2e:
     needs: changes
-    if: needs.changes.outputs.e2e == 'true'
+    if: needs.changes.outputs.native == 'true'
     runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:
@@ -518,7 +547,7 @@ jobs:
 
   windows-native-wrapper:
     needs: changes
-    if: needs.changes.outputs.e2e == 'true'
+    if: needs.changes.outputs.native == 'true'
     runs-on: windows-latest
     timeout-minutes: 20
     steps:
@@ -535,7 +564,7 @@ jobs:
 
   macos-native-wrapper:
     needs: changes
-    if: needs.changes.outputs.e2e == 'true'
+    if: needs.changes.outputs.native == 'true'
     runs-on: macos-latest
     timeout-minutes: 20
     steps: