feat(pi): first-class pi package with harness scaffolding and fleet subagent dispatch

[rafmacalaba]

Summary

Completes armada as a first-class pi extension and enables the fleet subagent workflow inside pi.

• pi extension (pi/extensions/armada.ts): new armada_dispatch LLM tool dispatches fleet roles (backend-dev, qa, adversary, ... or ship names galleon, corvette, ...) as isolated pi subprocesses — single {role, task} and parallel {tasks: [...]} modes (max 8, 4 concurrent) so the orchestrator can run independent phases concurrently. resources_discover contributes the 14 bundled skills + prompt templates (/voyage, /contract, /fleet, /armada-status) in armada-managed repos.
• Pi harness scaffolding: new project.harnesses manifest field (opencode default, pi opt-in, validated + deduped, rendered into armada.yaml). When pi is enabled, scaffold emits .pi/agents/<ship-name>.md per role: pi frontmatter (name, description, model where mappable), filled prompt body, and an Edit boundaries section derived from the permission matrix (pi has no SDK permission globs, so armada's file-ownership rules ride in the prompt body).
• Model mapping: openrouter/* IDs pin the subagent model; opencode-* IDs are opencode-only and are omitted so agents inherit the dispatching session's model.
• Uninstall removes armada-owned .pi/agents/ files.
• Docs: README pi integration section documents the dispatch tool and harness opt-in; TODO logs the Wave 2 item.

Verification

• Full suite: 605/605 pass, incl. 8 new tests in tests/pi-harness.test.js (manifest validation, renderer, scaffold/uninstall wiring).
• Extension loads under pi 0.84.3 (pi -e smoke run).
• Live end-to-end: scaffolded a temp repo with harnesses: ["opencode", "pi"], dispatched docs (single) and docs + architect (parallel) via armada_dispatch from a real pi session — both returned verbatim replies; parallel reported 2/2 succeeded.

[rafmacalaba]

Follow-up (4b82856): fleet defaults to OpenRouter in the pi harness

Previously pi subagents silently inherited the dispatching session's model (opencode-* IDs are unusable in pi, so budget tiers were ignored). Now:

• Every role maps to its catalog openrouter/* fallback in .pi/agents/<ship>.md frontmatter (galleon/xebec/frigate/bark → openrouter/deepseek/deepseek-v4-pro, commodore → openrouter/z-ai/glm-5.2, corvette → openrouter/xiaomi/mimo-v2.5, clipper/caravel → openrouter/minimax/minimax-m3).
• Scaffold writes .pi/settings.json with defaultProvider: "openrouter" + orchestrator model so the Commodore session defaults to OpenRouter too; uninstall removes the armada-owned keys.

Evidence: subprocess JSON events report the pinned model (deepseek/deepseek-v4-pro via OpenRouter); end-to-end armada_dispatch receipt for backend-dev returned OPENROUTER_GALLEON_OK at $0.0016/turn. Suite: 606/606.