Splits the model dropdown into a presentational 'ModelPicker' ('renderer/src/features/chat/components/model-picker.tsx') and keeps 'ModelSelector' as a thin wrapper that owns the chat-settings-specific glue (provider credential lookup, onOpenSettings wiring). The picker now accepts a plain 'value / onChange / onClear / onOpenSettings' interface so it can be reused outside the chat (agent form, future screens) without duplicating the grouped-by-provider layout and search filter.

Behavior unchanged: same grouping, same filter, same empty state, same provider credential gating.

Adds a full agents feature under '/playground/agents' with a list page, a detail page (system prompt rendered as markdown on the right, metadata on the left — same layout as the skill detail), and a dedicated form page for create and edit. Built-in agents are read-only and offer a 'Duplicate' action instead; custom agents can be renamed, have their instructions edited in either raw textarea or Streamdown-rendered preview mode, and opt into a built-in tool bundle via a picker that hides empty bundles (e.g. Planner) from the UI.

Routes are flattened with trailing underscores ('playground.agents_.$agentId.tsx', 'playground.agents_.$agentId_.edit.tsx') so the detail and edit pages render under '/playground' — which owns the '<Outlet />' — rather than trying to nest inside the detail route. 'renderer/src/route-tree.gen.ts' is regenerated accordingly.

Also adds an optional 'historyBack' prop to 'SkillDetailLayout' ('renderer/src/features/skills/components/skill-detail-layout.tsx', defaults to 'true' for backwards compatibility) so the agent detail can force the Back button to navigate to '/playground/agents' instead of popping browser history.

Adds an 'AgentSelector' to the composer ('chat-input-prompt.tsx'), placed first in the row so the spacing stays tight even when the container narrows, and tightens the MCP server selector / model selector sizing to match. Selecting an agent persists 'agentId' on the thread via 'use-playground-threads.ts'; new threads inherit the most recently used agent and fall back to 'ToolHive Assistant' when no selection has been made.

Also adds an 'Agents' link to the playground sidebar ('playground-sidebar.tsx') so the management page is reachable alongside 'New chat', 'Starred', and 'Recents'. Icons for 'New chat' and the agent picker are now vertically aligned so the sidebar rows don't jitter when the container is narrow.

Covered by new 'agent-selector.test.tsx' and updated 'playground-sidebar.test.tsx'.

The install dialog used to accept a single 'defaultReference' string which callers derived by concatenating 'name:version', producing invalid OCI references like 'github-release-notes@v0.0.4' and leaking a version-only value into the Name field. The dialog now takes 'defaultReference' (bare name) and 'defaultVersion' (tag) separately so each form field is pre-filled correctly.

Introduces a shared 'getBuildTitle' helper in 'renderer/src/features/skills/lib/build-reference.ts' and updates the local-build card and detail page to use it plus the new prop shape. Test coverage in 'card-build.test.tsx' is updated to assert the split values.

When the Skills Builder agent calls 'build_skill', the chat now renders a dedicated 'SkillBuildResultCard' right after the tool call instead of the raw JSON view. The card shows the skill name, description, version, tag, and a shortened digest with a tooltip, and exposes three actions: Install (opens the existing install dialog pre-filled with the bare Name and Version), View details (deep-links to the local build page), and Copy name (copies just the bare skill name).

Parsing lives in 'renderer/src/features/chat/lib/parse-skill-build-result.ts' and gracefully falls back to the generic tool renderer when the 'build_skill' output doesn't match the expected shape, so malformed or older tool responses don't break the chat.

The previous 'feat(playground): add agents management pages' commit
renamed 'playground.agents.$agentId.tsx' -> 'playground.agents_.$agentId.tsx'
and added 'playground.agents_.$agentId_.edit.tsx' but the two renamed
files never made it into the index, so clicking 'View details' or 'Edit'
on a custom agent rendered nothing. Add them so the flattened routes
resolve under '/playground' and actually mount.

The card used 'build.tag' verbatim, which is only a valid route param
when it matches a LocalBuild row in 'getApiV1BetaSkillsBuilds'. When the
list lookup in 'build_skill' lagged and we fell back to the user's
short input ('v0.0.4'), the navigate call hit /skills/builds/v0.0.4 and
404ed.

- Parser now preserves 'apiReference' and drops the 'reference' ('name:tag')
  fallback from 'build.tag' so the field only holds a real registry tag.
- Card navigates to 'apiReference' first and only falls back to 'build.tag'
  when it looks registry-prefixed (contains '/' or ':'); 'View details' is
  hidden otherwise instead of producing a dead link.
- 'build_skill' tool seeds the fallback 'LocalBuild.tag' with 'apiReference'
  instead of the user-supplied short tag, so future builds always emit a
  navigable tag even if the listing endpoint lags.

'DialogInstallSkill' was prefilled with 'version ?? tag', so a build
without an explicit version ended up with the full OCI reference
('localhost/my-skill:v1.0.0') dumped into the Version field. Drop the
'tag' fallback — if no version is set, leave the field empty so it
defaults to 'latest' on install.

Planner was instructions-only and not really useful in practice — it was
the sole reason the agent form needed a 'hasTools' filter on the tool
bundle picker. Remove the agent, its prompt, its reserved
'BuiltinToolsKey' variant, and the now-unused 'hasTools' field; simplify
the picker accordingly.

'seedBuiltinAgents' now deletes any leftover 'builtin.planner' row via a
new 'LEGACY_BUILTIN_AGENT_IDS' list so existing dev databases migrate
cleanly on startup.

'knip' flagged seven unused exports across the agents + model picker work.
Scope them to their own modules — no functional change.

…d agents flag gating

…away