feat(acp): advertise thought-level session config

[jakepresent]

Summary

• advertise ACP's standardized thought_level session config option from hermes acp
• map session/set_config_option for thought_level into AIAgent.reasoning_config
• return updated configOptions so ACP clients can refresh the selected value

Why

ACP v1 defines configOptions with category: thought_level for reasoning-level selectors. Hermes already has internal reasoning_config, but the ACP adapter did not advertise or apply that surface, so clients could not provide a real reasoning-effort dropdown.

Related work

• Related to fix(acp): honor agent reasoning config #30290, but not a duplicate: fix(acp): honor agent reasoning config #30290 makes ACP session creation honor existing persisted agent reasoning config. This PR exposes the ACP-standard client-controlled thought_level option and maps session/set_config_option back into that same internal reasoning_config.
• Also related to C:/Program Files/Git/model 选择器中增加思考模式（reasoning）的可视化配置 #25364's reasoning selector request, but this is scoped to the ACP adapter surface rather than Hermes' own /model UI.

Tests

• python -m pytest tests/acp_adapter/test_acp_commands.py::test_acp_new_session_advertises_thought_level_config_option tests/acp_adapter/test_acp_commands.py::test_acp_set_thought_level_updates_agent_reasoning_config tests/acp_adapter/test_acp_commands.py::test_acp_set_thought_level_none_disables_reasoning -q -o 'addopts='
• python -m pytest tests/acp_adapter -q -o 'addopts='

Live probe

Ran the ACP adapter from this worktree over stdio and verified session/new returns configOptions[thought_level] with current medium, and session/set_config_option to high returns the updated current value.

[alt-glitch]

Related: #30290 (fix(acp): honor agent reasoning config) and #25364 (reasoning-level selector request). Different mechanism — #30290 honors the existing internal reasoning_config, while this PR advertises the standardized ACP thought_level config option to clients and maps set_config_option back into reasoning_config. Complementary, not duplicate.

[tonydwb]

Code Review Summary

Verdict: Approved

✅ Looks Good

• Clean feature implementation: Advertises ACP's thought_level session config option and maps it to internal reasoning_config
• Well-scoped: Only 2 files (server.py + test), focused on a single concern
• Good test coverage: 3 new tests covering:
  • new_session returns the config option with correct default (medium)
  • set_config_option correctly maps high to reasoning_config = {"enabled": True, "effort": "high"}
  • none correctly sets {"enabled": False}
• Proper return value: set_config_option returns updated config_options so ACP clients can refresh — not ignored
• Follows existing patterns: _thought_level_current_value() mirrors the existing _edit_approval_policy_for_state() pattern
• No debug artifacts or secrets

Minor Note

• The parse_reasoning_effort import inside the elif block is fine (lazy import to avoid circular dependency)

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Reviewed by Hermes Agent

[teknium1]

Thanks for the focused ACP contribution. Current main confirms the feature gap: acp_adapter/server.py:1124-1131 exposes only models/modes, while set_config_option() returns no option state at acp_adapter/server.py:2045-2065.

Problems

• acp_adapter/server.py:537-540 documents that Zed renders config_options in the model-picker slot. Commit 029239860 intentionally moved edit approval from config options to modes to retain that picker. The added config_options responses would restore the same conflict.
• The new live-agent assignment is not durable. _persist() stores session metadata without reasoning_config (acp_adapter/session.py:424-449), _restore() recreates the agent without it (acp_adapter/session.py:544-552), and model switching replaces the agent (acp_adapter/server.py:2010-2017).
• Forks are also incomplete: fork_session() returns models/modes only (acp_adapter/server.py:1243-1247) and creates a fresh agent without carrying reasoning state (acp_adapter/session.py:252-264).

Suggested changes

• Preserve the Zed model-picker behavior while choosing the ACP representation for thought level.
• Make the setting durable across restore, model switch, and fork, with tests for each lifecycle path.

This is an automated hermes-sweeper review.

[teknium1]

Current main deliberately avoids config_options because Zed renders them in the model-picker slot (acp_adapter/server.py:537-540; commit 029239860). Adding this response field would reintroduce that picker regression; please use a representation that preserves model selection or gate it by verified client behavior.