- `bottle:` in agent frontmatter is now optional; agents without it
are portable and require bottles to be selected at launch.
- Adds `filter_multiselect` to `tui.py`: multi-select picker with
ordered selection list, Space/Enter to toggle, Ctrl-D to confirm.
- `ManifestIndex` gains `all_bottle_names` and `load_for_agent` accepts
`bottle_names: tuple[str, ...]` to merge bottles in order at runtime.
- `merge_bottles_runtime` in `manifest_extends.py` applies the same
field-merge rules as `extends:` to pre-resolved bottle objects.
- `BottleSpec` gains `bottle_names`; `_validate` and `write_launch_metadata`
thread it through so `resume` replays the same bottle configuration.
- `cmd_start` shows the bottle multiselect after agent selection,
pre-populated from the agent's `bottle:` field when present.
- Existing agents with `bottle:` declared continue to work unchanged.
Manifest.resolve() now returns an empty-dict manifest with only directory
paths recorded (home_md, cwd_md). No content is read from any .md file
until load_for_agent() is called for a specific agent at preflight.
- Manifest.from_md_dirs: scan-only, no frontmatter parsing
- Manifest.load_for_agent: parses the selected agent file and its bottle
chain; works on eager (from_json_obj) manifests too by returning self
- Manifest.all_agent_names: scans filenames in lazy mode
- backend._validate: calls load_for_agent and propagates upgraded spec
- cli/info.py, cli/list.py, cli/start.py: use load_for_agent / all_agent_names
- manifest_extends.py: reverted to original (no partial-resolve helpers)
- manifest_loader.py: only scan_agent_names + load_bottle_chain_from_dir
- Tests updated to call load_for_agent before accessing agents/bottles;
test_md_agent_repos_deferred renamed to test_md_agent_repos_fails_at_preflight
Broken bottle/agent files no longer block the agent selector or prevent
unrelated agents from loading. Per-file parse errors are collected in
`Manifest.broken_agents`; the CLI selector includes them via
`all_agent_names`, and the error surfaces only when the specific agent
is selected and launch is attempted (in `require_agent`/`bottle_for`).
Closes#236