chore(release): Bump version to 0.12.0

[arcaputo3]

Post-release default-version bump for the A2A orphaned-run revival seam (#66): new public A2AOrphanedRunReviver + A2AServerLive.Config.orphanedRunReviver, ResultManager.userMessage now Option, A2ARole derives CanEqual. Minor bump — additive public API.

The v0.12.0 tag (which drives the actual publish via PUBLISH_VERSION) is cut from the #66 merge commit; this PR just keeps the in-repo default in sync for local dev.

Consumer: TJC-LP/tjc-agents#115 (pins 0.12.0).

🤖 Generated with Claude Code

[claude]

Review: chore(release): Bump version to 0.12.0

Verdict: LGTM — the change is correct, minimal, and matches the stated intent.

What the diff does

Bumps the sharedPublishVersion fallback in build.mill from 0.11.0 → 0.12.0. Since PUBLISH_VERSION drives the actual publish (and the v0.12.0 tag is cut from the #66 merge commit per the description), this fallback only affects local publishLocal / dev builds. Correct behavior preserved: env var wins, default is now in sync.

• ✅ Code quality: single-line, idiomatic, no risk.
• ✅ Bugs/performance/security: none applicable to a version-string bump.
• ✅ Test coverage: N/A — no logic changed.

One consistency nit (non-blocking)

README.md still references 0.11.0 in the places consumers copy from, and there's no ### 0.12.0 Notes section, whereas prior releases kept these in sync:

• README.md:6 — baseline banner Scalagent \0.11.0``
• README.md:191 — ivy"com.tjclp::scalagent::0.11.0"
• README.md:197 — libraryDependencies += ... % "0.11.0"
• README.md:206 — <version>0.11.0</version>
• Missing a ### 0.12.0 Notes entry (0.11.0 and 0.10.x each have one).

I understand this PR is intentionally scoped to "keep the in-repo default in sync for local dev," so the README refresh may be handled separately. But since the install snippets are what downstream consumers (e.g. TJC-LP/tjc-agents#115, which pins 0.12.0) copy, bumping them here — or in an immediate follow-up — would avoid pointing new users at the prior version.

Nothing here blocks merge. 🚀