v0.9.1

Fixed

• Builtin agents were silently excluded from management listings, chain validation, and agent resolution. Added allAgents() helper that includes all three tiers (builtin, user, project) and applied it to handleList, findAgents, availableNames, and unknownChainAgents.
• resolveTarget now blocks mutation of builtin agents with a clear error message suggesting the user create a same-named override, instead of allowing fs.unlinkSync or fs.writeFileSync on extension files.
• Agent Manager TUI guards: delete and edit actions on builtin agents are blocked with an error status. Detail screen hides [e]dit from the footer for builtins. Scope badge shows [built] instead of falling through to [proj].
• Cloning a builtin agent set the scope to "builtin" at runtime (violating the "user" | "project" type), causing wrong badge display and the clone inheriting builtin protections until session reload. Now maps to "user".
• Agent Manager loadEntries suppresses builtins overridden by user/project agents, preventing duplicate entries in the TUI list.
• BUILTIN_AGENTS_DIR resolved via import.meta.url instead of hardcoded ~/.pi/agent/extensions/subagent/agents path. Works regardless of where the extension is installed.
• handleCreate now warns when creating an agent that shadows a builtin (informational, not an error).

Changed

• Simplified Agent Manager header from per-scope breakdown to total count (per-row badges already show scope).
• Reviewer builtin model changed from openai/gpt-5.2 to openai-codex/gpt-5.3-codex.
• Removed code-reviewer builtin agent (redundant with reviewer).