release: decide v1.0 timing for @agentskit/core (Phase 1 review gate)

[EmersonBraun]

Context

`docs/PHASE-1-REVIEW.md` (line 164) lists this as an open gate before Phase 1 can officially close:

Consider whether the @agentskit/core major bump is the moment to publish v1.0 on core, or defer

Phase 1 is feature-complete (all 20 user stories closed in issues #114–#133). The pending changeset for `@agentskit/core` is a major (removed `createFileMemory` + `loadConfig` for browser compat per ADR 0001). Either:

• Bump to 1.0 now and treat the removal as the v1.0 surface — the contracts are formally frozen (RFC-0007), bundle/coverage gates are active, the surface is what we want to commit to.
• Defer to 0.x major — bump core to 0.next.0 and reserve 1.0 for a coordinated launch milestone (Phase 0 [P0.52] Coordinated launch (HN + Twitter + ProductHunt + Reddit) #263).

What to decide

1. Pick one of the two paths.
2. Document the decision in an ADR (`docs/architecture/adrs/0011-core-v1-timing.md` or similar).
3. Update the pending changeset to match.
4. If 1.0: write a "core v1.0" announcement page in docs (extend `docs/get-started/announcements/core-v1.mdx` which already exists as a stub).
5. If deferred: open a tracking issue for the eventual 1.0 cut alongside the launch.

Why this matters

Phase 1 → Phase 2 gate explicitly requires the 20 stories to be done or de-scoped. They are done. This is the last open item before that gate flips. Holding it open blocks downstream sprint planning for S10+.

Acceptance

• Decision recorded in an ADR
• Pending changeset reflects the chosen version bump
• If 1.0: announcement page filled out + RFC-0007 contract freeze cross-linked
• PHASE-1-REVIEW.md gate item ticked

[EmersonBraun]

This is a meta / planning issue (RFC, plan refresh, release-timing decision) that needs maintainer judgement and stakeholder input rather than code changes. Leaving open.