fix(code): preserve fleet worktrees with per-worktree config

[danii1]

Summary

• migrate a bare clone's core.bare=true into its main-worktree config before enabling extensions.worktreeConfig
• self-heal existing fleet clones during worker repository initialization
• add regression coverage for bare-clone worktrees and already-poisoned workspace state
• document the fix in the changelog

Root cause

Hook isolation enabled per-worktree Git config in the shared bare clone while leaving core.bare=true in shared config. Git then treated every linked task/review worktree as bare and rejected checkout, reset, clean, and merge with this operation must be run in a work tree.

Validation

• pre-commit: format, lint, typecheck
• pre-push: full monorepo test suite and typecheck
• @getdevintern/code: 1296 tests passed