Document the workflow-deploy-source / workflow_run_launch_spec overlap

[TheGreatAxios]

CL-7271.

Analysis lane. The ticket's premise — that @corbits/workflow-deploy-source duplicates Interchange's workflow_run_launch_spec and can be deleted — does not survive reading the native writer.

The two tables share a key and several columns but encode opposite recovery models:

• Native freezes. frozen_approval_bundle replays the approval verbatim, no re-probe. Written only by prepareExclusiveDeployment, read only by deployReadyAllocation, both in workflow-allocation-service.ts. Exclusive-only because it exists to survive an allocation being replaced.
• Ours re-resolves. Records where the bytes came from and re-derives against the live catalog at redeploy.

That trade-off is the one CL-6687 (rotated keys never reaching live agents) was fixed in favour of re-resolution, and the one restoreDeploymentFromRecord decides the same way via "deferred-to-wake" (CL-6648). Adopting native wholesale would reverse both.

Recommends keeping both with a documented split, rather than deleting ~350 loc that turns out not to be redundant.

Two original observations survive: the missing FK on anchor_run_id (belongs to CL-7258), and the four columns with no native counterpart (entry, pin, definition_asset_id, source_ref).

Docs only. No code change. Draft — not for merge.

[TheGreatAxios]

Consolidated into #531 — four independent docs files merging as one CI cycle rather than four serialized ones under strict branch protection. Content unchanged.