feat(claude-code-cli): add the pi:interactive native target

[goldmedal]

Why

GenBI wants a vendor-neutral native session runtime for API-key vendors (anything other than Claude Code and Codex). The pi coding agent (earendil-works/pi) fits that role, but it ships no permission system: it executes every tool call with the account's OS permissions. A Warble target for pi therefore has one job — author a launch contract that leaves the session nothing but the host-owned MCP server, and refuse every shape it cannot keep inside that contract.

What

A fifth native target, pi:interactive, folded into the warble binary next to codex:interactive.

• warble dispatch ir.json --target pi:interactive --purpose analysis --native-scope scope.json --native-mcp mcp.json --pi-model <provider>/<model-id> --out <cwd> emits:
  • .warble/pi/SYSTEM.md — the authored system prompt (brief + analysis prompt fragment + scope/safety instructions + the shared persistence/presentation/dashboard instructions), handed to pi through --system-prompt, which replaces its default prompt;
  • .warble/pi/agent/settings.json and .warble/pi/agent/mcp.json — the server-owned pi agent directory (PI_CODING_AGENT_DIR). Project trust is refused, telemetry is off, pi's own retries are off, and the MCP credential is referenced through ${WARBLE_MCP_CONNECTION_CREDENTIAL} so the file never carries it (same posture as Codex's bearer_token_env_var);
  • RUN.md, .warble/interactive-launch.json (v4, or v5 with --native-host) and .warble/interactive-ownership.json.
• The launch spec's argv starts an RPC session with every pi discovery mechanism switched off by name and an explicit --tools mcp__genbi_session__… allowlist. --no-tools is deliberately not used: it also drops MCP tools. The spec's new pi object carries the one-shot JSON-mode argv (prompt positional after --), the first prompt for the RPC prompt command, the agent directory, the required environment, and the minimum pi version (1.0.4, the first release whose --tools keeps MCP tools when named).
• Capability profile: analytical capabilities are realized through the host MCP server; mutation, approval, repository-read and setup/enrichment capabilities fail loudly; divergent step tiers degrade to the single session model unless a --native-host plan runs the steps.
• Wall-hits, each named: any purpose other than analysis, a missing --native-mcp, a missing or malformed --pi-model, --provider fragments, scope entry, component composition without a host, and any component whose shape no host MCP tool serves.

No existing target's output changes; claude-code:* and codex:interactive launch specs are byte-identical to before (the only shared-code change threads an optional pi input through the launch-spec renderer).

Verification

Gate	Result
cargo fmt --all --check	PASS
cargo clippy --workspace --all-targets --locked -- -D warnings	PASS
cargo build --workspace --locked	PASS
cargo test --workspace --locked	PASS (see summary below)
RUSTDOCFLAGS=-D warnings cargo doc --workspace --no-deps	PASS
cli/tests/pi_interactive_dispatch.rs (8 tests)	PASS
cargo build --release -p warble-cli + just install-ts lint-ts test-ts build-ts	PASS
just install-codex-ts lint-codex-ts test-codex-ts build-codex-ts	PASS
just install-bird-eval lint-bird-eval test-bird-eval build-bird-eval	PASS
just publish-check	PASS
actionlint	not run locally (no workflow file is touched)

What I did not exercise:

• No pi process is started by these tests or by Warble; the argv/env contract was measured against pi 1.0.4 separately (closed launch, --tools allowlist semantics, env-var interpolation in mcp.json, RPC lifecycle). A comma-separated --tools list with several exact names was not part of that measurement; only a single exact name and a mcp__* glob were.
• The --native-host (v5) path for pi is covered by the shared host validation and plan writing, not by a pi-specific live test.
• The TypeScript back-ends are untouched.

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