Keep removed worktrees retired and simplify agent changes

[eivindjonassen]

Summary

• Keep confirmed-missing worktrees excluded across refreshes, reconciliation, and returning to a project. Generic events previously overrode retirement, and refreshes could bypass pending directory checks.
• Check historical directories through the live project root before resolving their locations. Wait for active-session checks before querying historical locations.
• Preserve genuine permission and form attention through volatile cache hints and authoritative REST reconciliation.
• Show steering controls only for user prompts. Internal Build/Plan reminders remain server-owned inbox work.
• Display agent changes inline, such as 'Agent changed to Plan', without Show/Hide controls.

Verification

• Reproduced removed-worktree resurrection and internal-reminder steering cards with failing regression tests before fixing them.
• fnm exec --using=26.7.0 pnpm check passed on the latest main base, including 403 mobile tests and both native bundle exports.
• fnm exec --using=26.7.0 pnpm native:doctor passed all 18 checks.
• Tests cover refresh and remount, fresh attention at retired locations, retirement after empty REST snapshots, and real user steering prompts alongside internal reminders.
• Physical-device verification of the latest changes remains pending.

Published preview

These UI fixes were published locally to preview for iOS and Android, runtime 0.1.5:

https://expo.dev/accounts/omnicus/projects/o5s-code/updates/6b09da96-1562-4e95-b48a-5e3133b7c48e

The PR is based on current main and was rechecked with its OpenCode client 2.0.19 dependency. The linked OTA was published before rebasing onto that dependency update.