Adopt labkit engine for Intelligence Flow sync

[bigboateng]

What

Replaces the hand-authored sync-upstream.yml with the version-controlled control
plane generated by labkit upstream. Projection is now driven by the shared
engine (python -m labkit project) from publish.config.json.

Why

Unifies Boatstack's projection with Pitot and Value Map on one reviewed, drift-gated
engine. Boatstack keeps its bespoke build logic upstream via .labkit/hooks.py
(build_files), so the projected output is unchanged.

Notable changes

• Projection body: python3 …/build_boatstack.py --write → python -m labkit project.
• Adds Python setup + pip install ./intelligence-flow/labkit.
• Append-only release-note gate on the sync PR is preserved (same semantics).
• Deterministic cron (2 */6).

Merging installs the workflow; the projected surface is byte-for-byte identical
(asserted by the upstream golden reproduction test). No --adopt needed — this repo
already carries a projection-style UPSTREAM.json.