Host verb table declared in plugin-hostd; build the required verbs; limits as declared defaults #131

Job: declare the host verb table in plugin-hostd's own protocol declaration and build the verbs that are required and missing.

Ruled by the operator 2026-10-21 (openmixer docs/design/specs/2026-10-21-strip-declaration.md on lane/strip-declaration-spec, section 14 items 20 to 23).

1. A verbs table in plugin-hostd's protocol declaration (protocol/plugin-hostd.json family): each of the 35 mod-ui host verbs with required / optional / absent per profile (LV2 worker, CLAP worker, console). Starting values, read from docs/zynthian/verbs.tsv on the devel/zynthian branch:
   • required: add, remove, bypass, connect, param_set, state_load, state_save, state_tmpdir, feature_enable, bundle_add, bundle_remove, preset_load, preset_save, preset_show, transport, transport_sync, cpu_load
   • optional: midi_learn, midi_map, midi_unmap, cv_map, cv_unmap, monitor_midi_program, monitor_output, output_data_ready, patch_get, patch_set
   • absent on purpose: cc_map, cc_value_set, cc_unmap, hmi_map, hmi_unmap, show_external_ui, set_midi_program_change_pedalboard_bank_channel, set_midi_program_change_pedalboard_snapshot_channel
2. Build the required verbs that the tsv shows broken on the CLAP worker (connect port names, param_set by symbol, state_load, state_tmpdir, feature_enable, bundle_add/remove replay, preset_load/save/show). The smallest fix and its location (plugin-hostd or omx-clap-host) are in the tsv's last column; split the omx-clap-host parts into omx-clap-core issues.
3. Limits as DECLARED DEFAULTS, written once and generated: pool members 8 per format, chain members at least 1 (a chain of one is valid, so a trip of one isolated plugin is a chain of one), 64 words in one line, the chain codes. Floor 1 overrides the draft's 2 on Protocol: declare a chain of instances run in one worker, with crash quarantine (for omx-clap-core#104) #101.
4. A contract test that the served verb answers match the table; sabotage-verify (change a required verb to absent, watch it go red).

Rules: commit small, author Pau Aliagas linuxnow@gmail.com, no trailer, PR open, do not merge. Hand back what could not be run.

SCOPE UPDATE (operator 2026-10-21, binding; supersedes anything above that differs)

Model: own / pool / chain as BUILT in plugin-hostd 0.7.0 (#101, docs/design/notes/2026-10-21-chains.md on wave/contract-one-pass). NO pool of chains. mod-host is to be dropped: the host is omx-clap-host plus the LV2 adapter only.

1. Chain floor 1. A chain of ONE member is valid (a trip of one plugin maps like any other). The built grammar refuses fewer than two with -902: change the grammar, the refusal, tests/verbs_contract.py, README and the protocol declaration, and make omx-clap-host accept a chain line of one (coordinate through a comment on omx-clap-core#104; do not edit that repo here). Limits (pool members 8, chain members at least 1, 64 words in a line, chain codes) are DECLARED DEFAULTS in the declarations.
2. LV2 chains under require_pins (a precondition of removing mod-host, openmixer#2052). While require_pins is on a chain of LV2 is refused (PLACEMENT_INVALID) because an LV2 pin holds only in a world narrowed to the plugin's own bundle. Build the chain note's proposal: a chain's worker gets a world narrowed to the UNION of its members' bundles (the format's narrow_world takes a list of uris), so each member's pin still holds. Prove it with a chain of LV2 members through the adapter under require_pins, and sabotage-verify (break the union, watch it go red). Bench with omx-clap-core#104's eight LV2 plugins through the adapter and report the numbers.
3. The verb table (required / optional / absent per profile) as in the body above.
   Work on plugin-hostd's wave/contract-one-pass (tip 83e54db) via a lane branch; it joins GATE 0.3 only if the lead says so, otherwise it lands after the batch (GATE 2). No PR, no merge. Comment on this issue, do not open new issues.

OPERATOR RULING 2026-10-22: the Zynthian gaps are FIXED, not tolerated

Source: docs/zynthian/engine-gaps.md on spike/zynthian-strip (plugin-hostd PR #129) and docs/zynthian/verbs.tsv on devel/zynthian. The gaps the table calls "use" (the chain runs, a user loses a feature) become required work, not optional:

1. Presets: save, rename, delete, user banks. preset_save, preset_show, preset_load and the bundle verbs on both CLAP and LV2 workers (verbs.tsv: CLAP answers -902 today; omx-clap-host writes the plugin's state as a preset file and loads it via the CLAP preset-load extension). Zynthian side: the plugind engine lists, saves, renames and deletes user presets as jalv does.
2. Parameter feedback (a plugin moves its own control: automation, an LFO, a preset load). The worker reports the change, the daemon forwards it as an event (today output_set carries meters only), and the Zynthian engine updates its controller. omx-clap-host: CLAP params flush out-events to the host.
3. MIDI learn. midi_learn, midi_map, midi_unmap (and cv_map/cv_unmap) answered by the CLAP worker (verbs.tsv: -902 today); Zynthian's own learn by controller keeps working and stays the surface.
   These move from "optional" to "required" in the verb table for the CLAP worker and the Zynthian profile. Order: the chain model first (S0 done, Run mod-host in CI so the LV2 worker path is proven #104, floor 1, union-narrowed world), these directly after. Lanes: omx-clap-core (worker side), plugin-hostd (relay + table), the Zynthian engine patch on PR Zynthian spike: a chain's audio slots as a plugin-hostd strip, parallel slots through an explicit mix #129's branch. Comment here; open no new issue.