fix: land post-#996 cache-path and soldr pin follow-ups

[zackees]

Context

PR #996 merged and auto-closed #994/#995 before the follow-up commits for the failed post-merge checks landed on main.

The remaining work is concrete:

• Check (macos-latest) failed the new project-name-invariant cache tests because macOS temp paths can canonicalize through a different prefix (/private/var/...) than the project path used for relativization.
• Several workflows and the board-build template were still on zackees/setup-soldr@v0.9.65, and the native-build template still pinned soldr 0.7.98 even though the current upstream releases are setup-soldr v0.9.66 and soldr v0.8.0.
• The repo Docker helper images under ci/docker-* also still pinned SOLDR_VERSION=0.7.98.

Proposal

• Canonicalize the compile CWD before stripping absolute compile args to project-relative paths, and cover the macOS-style symlink/canonical-path mismatch with a regression test.
• Pin all setup-soldr workflow uses to v0.9.66 and explicitly request version: 0.8.0.
• Bump the repo Docker soldr release pins to 0.8.0.

Acceptance criteria

• A follow-up PR lands the two missing commits on main.
• Check (macos-latest) passes the cache-key invariance tests.
• Board-build workflows use setup-soldr@v0.9.66 and soldr 0.8.0.
• rg '0\.7\.98|0\.7\.92|v0\.9\.65|v0\.9\.64|setup-soldr@v0\.9\.65' .github ci returns no remaining stale pins.
• uv run --no-project python ci/render_workflows.py --check passes.

Related issues

• Follow-up to ci(dylint): decide and enforce Dylint as a required status check #994, perf(build): decide fate of core-cache-hydrate after fw-libs zccache fix #995, and fix: require Dylint and repair core cache hydration #996.