ci: fix clang-tidy-diff path mismatch between RunsOn and GitHub-hosted runners

The gate job runs on RunsOn/AWS where GITHUB_WORKSPACE is /__w/...
The annotation job runs on ubuntu-latest where it is /home/runner/work/...

compile_commands.json bakes in absolute paths from the gate runner.
When clang-tidy-diff invokes clang-tidy on the annotation runner, it
reads the "directory" field and calls chdir() on the AWS-style path
which does not exist, causing a silent crash and empty fixes.yml.

Rewrite the workspace prefix in compile_commands.json before invoking
clang-tidy-diff so paths resolve correctly on the annotation runner.

Author: mrpollo

.github/workflows/ci-orchestrator.yml

@@ -814,10 +814,28 @@ jobs:
 
       - name: Analysis - Run clang-tidy-diff and export fixes
         run: |
-          # clang-tidy uses the absolute build dir from compile_commands.json to chdir.
-          # That path (/__w/.../build/...) doesn't exist here — symlink it to our workspace.
-          sudo mkdir -p /__w/PX4-Autopilot
-          sudo ln -sfn ${{ github.workspace }} /__w/PX4-Autopilot/PX4-Autopilot
+          # WHY WE REWRITE compile_commands.json PATHS
+          #
+          # The clang-tidy gate job runs on a RunsOn/AWS runner where the workspace
+          # root is "/__w/PX4-Autopilot/PX4-Autopilot". All absolute paths baked
+          # into compile_commands.json (the "file" and "directory" fields, and every
+          # -I include path in "command") use that prefix.
+          #
+          # This annotation job runs on a GitHub-hosted runner where the workspace
+          # root is "/home/runner/work/PX4-Autopilot/PX4-Autopilot". When
+          # clang-tidy-diff invokes clang-tidy, it reads the "directory" field from
+          # compile_commands.json and calls chdir() on it. Since the AWS-style path
+          # does not exist here, clang-tidy crashes with:
+          #   LLVM ERROR: Cannot chdir into "/__w/.../build/px4_sitl_default-clang"
+          # and silently produces an empty fixes.yml — so no annotations are posted.
+          #
+          # Fix: rewrite all occurrences of the AWS workspace prefix to the current
+          # runner workspace ($GITHUB_WORKSPACE) before invoking clang-tidy-diff.
+          # This is safe because compile_commands.json is a local scratch file we
+          # downloaded from the artifact; we are not modifying any source file.
+          sed -i "s|/__w/PX4-Autopilot/PX4-Autopilot|${GITHUB_WORKSPACE}|g" \
+            build/px4_sitl_default-clang/compile_commands.json
+
           mkdir -p clang-tidy-result
           git diff -U0 origin/${{ github.base_ref }}...HEAD \
             | clang-tidy-diff-18.py -p1 \