fix(acp): honor configured max turns

[lxy271713]

What does this PR do?

ACP sessions now honor the existing agent.max_turns setting when constructing
AIAgent. Previously, SessionManager._make_agent() omitted max_iterations,
so ACP always used the agent constructor default even when a profile configured
a smaller turn limit.

The setting is forwarded only when it is a positive integer. Missing or invalid
values remain omitted, preserving the existing AIAgent default and avoiding a
second copy of that default in the ACP adapter.

This is intentionally separate from #64045 and the other open ACP toolset PRs;
it does not change ACP tool selection.

#67696 proposes a shared resolver with additional unlimited/string spellings but
does not currently update ACP. This patch targets main's positive-integer
contract; if #67696 lands first, the ACP read can switch to that resolver during
rebase instead of keeping the local validation.

Related Issue

No linked issue. Related but non-overlapping: #64045 configures the ACP tool
surface, and #67696 proposes broader turn-limit parsing. This PR only propagates
the existing turn limit into ACP agent construction.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Security fix
• Documentation update
• Tests (adding or improving test coverage)
• Refactor (no behavior change)
• New skill (bundled or hub)

Changes Made

• Read agent.max_turns in acp_adapter/session.py.
• Pass valid positive integers to AIAgent as max_iterations.
• Preserve the existing constructor default for missing, boolean, string, zero,
  negative, or otherwise invalid values.
• Add regression coverage for the configured and fallback paths.

How to Test

1. Run TMPDIR=<non-sensitive-path> uv run --isolated --frozen --extra acp --extra dev pytest tests/acp tests/acp_adapter -q.
2. Confirm all 338 tests pass.
3. Run uv run --isolated --frozen --extra acp --extra dev ruff check acp_adapter/session.py tests/acp/test_session.py.

Checklist

Code

• I've read the Contributing Guide.
• My commit message follows Conventional Commits.
• I searched existing PRs and kept this change separate from the open ACP toolset work.
• My PR contains only changes related to this fix.
• I've run pytest tests/ -q across the entire repository.
• I've added tests for my changes.
• I've tested on macOS 26.5.1.

Documentation & Housekeeping

• Documentation update: N/A; this uses the existing agent.max_turns setting.
• cli-config.yaml.example: N/A; no config key was added or changed.
• CONTRIBUTING.md / AGENTS.md: N/A; no architecture or workflow changed.
• Cross-platform impact considered: the change is platform-neutral config propagation.
• Tool descriptions/schemas: N/A; no tool behavior changed.

Screenshots / Logs

Not applicable. The regression is covered by constructor-argument assertions and
the complete ACP/ACP-adapter test suites.

[teknium1]

Thanks for isolating the ACP configuration propagation fix. The source change addresses a current-main omission: acp_adapter/session.py:623-651 constructs AIAgent without max_iterations, despite agent.max_turns defaulting to 500 in hermes_cli/config_defaults.py:32.

Problems

• The test hunk is anchored at tests/acp/test_session.py:439 from the PR base, but current main's file ends at line 329 after 39975613b13b418e0eceda178434d7be90ad4f91; GitHub reports the PR as conflicting.

Suggested changes

• Recreate the parameterized regression coverage in the current test-file layout while preserving the positive-integer and invalid-value cases.

Automated hermes-sweeper review.