feat: multi-ACP team template (proto + claude) + coder escalation

[mabry1985]

Summary

• examples/team-template/langgraph-config.yaml is now a proper multi-ACP recipe: it
  declares both supported ACP coders — proto (proto --acp) and claude
  (claude-code, the adapter alias for claude-agent-acp, which takes no launch args)
  — and enables the coder plugin (ADR 0064) alongside delegates + project_board.
• project_board.coders is now a smart: proto → reasoning: claude model-tier ladder
  over the two ACP agents (was a single-coder fast/smart: proto ladder).
• Added a coder: config block (delegate: proto) + a comment explaining it's the
  execution-grounded search-ladder escalation (greedy → best-of-k → tree-search) for
  hard, verifiable features the coders ladder above still can't pass — a different axis
  than model-tier escalation, and only for a trusted model/host (subprocess isolation,
  not a true sandbox).
• Added a "Team template" field reference to README.md: every section of the
  shipped template explained (sentinels, identity/model gateway-inherit,
  agent_runtime, the two ACP delegates, project_board.coders + how tier-escalation
  works, the coder plugin as the search-ladder escalation, filesystem), cross-linking
  ADR 0055 (multi-team) and ADR 0064 (coder).
• Extended tests/test_team_spawn.py with a content contract over the shipped template
  (parses; declares delegates/project_board/coder; both ACP delegates with the
  right command/args/workdir; the smart→reasoning coders ladder; coder.delegate
  points at a declared delegate; filesystem fenced to {{REPO}}) so a future edit can't
  silently drop a delegate or break the ladder.
• Bumped portfolio to 0.15.0 (manifest + pyproject, kept in lockstep per
  tests/test_packaging.py). No CHANGELOG file exists in this repo, so none was added.
• secrets.example.yaml next to the template was left untouched — it doesn't reference
  delegates.

Gate output

=== ruff check . ===
All checks passed!
=== ruff format --check . ===
8 files already formatted
=== pytest -q ===
........................................................................ [ 57%]
.....................................................                    [100%]
=============================== warnings summary ===============================
.../fastapi/testclient.py:1: StarletteDeprecationWarning: Using `httpx` with
  `starlette.testclient` is deprecated; install `httpx2` instead.
    from starlette.testclient import TestClient as TestClient  # noqa

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
125 passed, 1 warning in 2.13s

(125 = 119 pre-existing + 6 new shipped-template content-contract tests. Ran with
pip install -r requirements-dev.txt ruff==0.15.10 on Python 3.12, matching
.github/workflows/ci.yml.)

Test plan

• ruff check . clean
• ruff format --check . clean
• pytest -q — 125 passed
• examples/team-template/langgraph-config.yaml parses and matches the spec
  (verified inline + via the new tests)
• Reviewer: confirm the coder.delegate: proto default reads sensibly, and that
  pointing users at docs/adr/0055-*.md / docs/adr/0064-*.md in the main
  protoAgent repo is the right cross-link convention for this plugin repo

🤖 Generated with Claude Code