feat(local-agent): support OpenCode and Oh My Pi

[jmagly]

Summary

• add OpenCode and Oh My Pi to local-agent discovery, readiness, provider metadata, and the War Room
• drive both CLIs non-interactively over stdin with underlying model passthrough
• keep T3MP3ST's Arsenal as the execution boundary by denying OpenCode permissions and passing --no-tools to Oh My Pi
• document the supported agents and add regression coverage for native install paths, auth artifacts, argv, stdin, model routing, and tool isolation

Verified integration contracts

• OpenCode: opencode run, stdin prompt, --model provider/model, auth presence at its documented data path, and OPENCODE_PERMISSION={"*":"deny"}
• Oh My Pi: piped-stdin print mode, --model, --no-tools, and local auth database presence

Verification

• npx vitest run src/__tests__/local-agent-path-resolution.test.ts src/__tests__/local-agent-provider.test.ts src/__tests__/local-agent-tool-calling.test.ts — 60 passed
• npm test — 753 passed plus ops/model-matrix/frontier self-tests
• npm run typecheck
• npm run lint — 0 errors (pre-existing warnings only)
• npm run build
• npm run test:gate — 5/5
• git diff --check

Closes #136

[jmagly]

Reviewed PR #144 at 69a8c579b5c074622f1f4d6d64ffc0e86d929e86.

No blocking findings.

Public-input threat preflight: pass. The issue, PR body, commit metadata, patch, and thread contain no policy-override, credential-exfiltration, hidden-command, or test-bypass instructions.

Security boundary:

• OpenCode receives a process-local OPENCODE_PERMISSION={"*":"deny"} override on both one-shot and backbone paths.
• Oh My Pi receives --no-tools on both paths.
• Provider keys remain stripped from child environments; each CLI continues to use only its own login.
• Runtime tests verify argv, environment policy, stdin transport, auth-artifact readiness, and model routing.

Verification:

• Hosted T3MP3ST CI: pass.
• Focused local suite: 60 passed.
• Full local suite: 753 passed plus auxiliary self-tests.
• Typecheck, build, lint (0 errors), provenance spine gate, and diff check: pass.

Residual risk:

• These adapters depend on upstream CLI flag/environment contracts; regression fixtures pin the currently documented behavior.

Maintainer-owned PR: recorded evidence here instead of self-approval. Exact head is merge-ready.