[gh-aw] Eliminate magic GH_AW_* secret references from lock files (#11685)

The dotnet/android secret-audit report flags every secret name that appears
in a compiled workflow, including the "magic" fallback secrets that gh-aw
emits as the tail of its token-resolution chain (`GH_AW_GITHUB_TOKEN` and
`GH_AW_GITHUB_MCP_SERVER_TOKEN`). Those names showed up in both
`*.lock.yml` files even though we never set those secrets in the
`copilot-pr-reviewer` environment, because gh-aw bakes the full fallback
expression into every safe-output handler and into the GitHub MCP server
wiring.

Set explicit `github-token: ${{ secrets.GITHUB_TOKEN }}` overrides at two
levels so the compiler short-circuits both fallback chains before they
reference the magic names:

  - `safe-outputs.github-token` -> replaces the
    `safe-output.github-token` -> `GH_AW_AGENT_TOKEN` ->
    `GH_AW_GITHUB_TOKEN` -> `GITHUB_TOKEN` chain that safe-output handlers
    (`create-issue`, `create-pull-request-review-comment`,
    `submit-pull-request-review`) use.

  - `tools.github.github-token` -> replaces the
    `GH_AW_GITHUB_MCP_SERVER_TOKEN` -> `GH_AW_GITHUB_TOKEN` ->
    `GITHUB_TOKEN` chain that the GitHub MCP server container uses.

The existing `assign-to-agent.github-token: ${{ secrets.ANDROID_TEAM_PAT }}`
override is left alone -- the Copilot assignment API requires a user-owned
fine-grained PAT and rejects `GITHUB_TOKEN`.

`GITHUB_TOKEN` is the correct choice (not `COPILOT_GITHUB_TOKEN`) for these
overrides because `COPILOT_GITHUB_TOKEN` is scoped to "Copilot Requests:
Read" only -- it has no `issues: write` / `pull-requests: write` scopes and
would 403 on every safe-output write. The safe-output processing jobs that
gh-aw generates run with their own elevated `permissions:` block, so the
default `GITHUB_TOKEN` already has the scopes they need.

After recompiling, the `# Secrets used:` block (and the machine-readable
`gh-aw-manifest:` JSON) in each lock file lists only secrets that are
actually configured:

  nightly-fix-finder.lock.yml:  ANDROID_TEAM_PAT, COPILOT_GITHUB_TOKEN,
                                GITHUB_TOKEN
  android-reviewer.lock.yml:    COPILOT_GITHUB_TOKEN, GITHUB_TOKEN

`gh aw compile` reports 0 errors / 0 warnings on both workflows.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jonathanpeppers

.github/workflows/android-reviewer.lock.yml

@@ -28,11 +28,13 @@ network:
     - "vsassets.io"
 tools:
   github:
+    github-token: ${{ secrets.GITHUB_TOKEN }}
     toolsets: [pull_requests, repos]
     # Allow reading PR content from external/first-time contributors.
     # The /review command is gated to maintainers, so only trusted users can trigger it.
     min-integrity: none
 safe-outputs:
+  github-token: ${{ secrets.GITHUB_TOKEN }}
   create-pull-request-review-comment:
     max: 50
   submit-pull-request-review: