Governance: provision validated proposal-type contracts through library workspaces

[adrianwebb]

Objective

Complete the missing governed authoring path discovered during SDK #293 / Platform #501 acceptance. Proposal publishing requires .treeseed/governance/proposal-types/.yaml, but library workspace write only handles book/page, agent-profile and operational-content. Do not bypass TreeDX or add hardcoded fallback types.

Interfaces and gates

• Accept a typed proposal-type workspace write through existing authorization, version and idempotency boundaries.
• Validate SDK ProposalTypeContract, exact canonical path/id match, source text, create/update collision and expected SHA.
• Apply through existing text changeset, audit, submit and governed staging publication.
• Tests reject invalid schema, path escapes/mismatched IDs, stale versions and unauthorized writes; valid create/update read-back.
• Provision SDK implementation type through the normal library workflow and retry real proposal publication.
• Investigate and wire exact proposal-type contract indexing into workday planning snapshots; reject missing contracts instead of silently inventing policy.

Dependencies

API #334 / PR #335 repair false replay and missing-contract diagnostics. Existing draft48d5429f-4882-4e89-824e-1866e70e7adb and empty workspace d61b76c1-c48f-4dd4-878c-22321ec2b730 are retained.

Rollback

Revert owner implementation only; preserve authored contracts, proposals, candidates and audit. No direct protected-ref push, fake estimates, database insertion, purge or credential changes.

Evidence

Gate	Evidence	Status
Missing authoring route	API staging330b0d5, knowledge-workspace-service.ts	Confirmed
Test / live publication	Pending	Pending