[ernestprovo23]

Adds an additive agentic tool-calling surface to the provider adapter protocol. Prerequisite for DSE TUI P0 (DSE-1807).

What changes

• ToolSpec, ToolCall, AgenticResponse dataclasses in adapters/base.py.
• Neutral content blocks (text / tool_call / tool_result) with assistant_tool_call_message() and tool_result_message() helpers; each adapter translates to its own wire shape.
• supports_tool_calls class flag. The agent loop must check it — capability is never inferred from a model name.
• build_request / stream_request gain tools and tool_choice; messages widened to list[dict] so content may be a block list.
• New parse_agentic_response() — parse_response() -> tuple[str, TokenUsage|None] cannot express a tool call, so this is parallel rather than a breaking change.
• Anthropic adapter implements the surface (tool_use / tool_result, tool_use_id carried end-to-end, stop-reason normalization, parallel calls preserved in emission order). OpenAI-compat and Gemini declare supports_tool_calls = False and raise ProviderError.
• tools and output_contract are mutually exclusive — raises ValueError. Forced-tool structured output and agentic tool calling are different modes; parse_agentic_response never consults forced-tool state.

Additive guarantee

String-content request bodies are byte-identical to before. Asserted by test_string_content_body_is_unchanged_by_the_new_surface; the pre-existing suite required zero changes.

Verification (builder, fresh)

• 870 passed in 37.97s — full suite
• 28 passed in 0.08s — tests/test_agentic_tools.py
• ruff check src/conclave tests — All checks passed
• ruff format --check — 6 files already formatted

Release control

Classifies security-specific on accumulated keywords only: the sole trigger is redact appearing on a changed line because adding five names re-wrapped a one-line import in adapters/__init__.py. redact() is unchanged; every other file classifies routine-non-security in isolation. Receipt granted by Ernest Provo in authenticated session at head SHA d3603f7b706cf9dd2cd7445b1f96b7a101f4e7b8.

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https://claude.ai/code/session_01H5GFPdJDb2VEuqv7X8Wn6E