feat: normalize provider tool specifications

[hallerite]

Summary

• add one canonical normalization boundary for client-executed JSON-schema function tools
• accept legacy/verifiers, OpenAI Chat Completions, OpenAI Responses, Anthropic, MCP, Gemini-compatible, and Pydantic-style inputs
• integrate normalization across every renderer and schema-aware response parser
• reject hosted, custom-text, namespace, shell, computer, and other non-function protocols with an explicit capability error
• preserve the existing Chat-style rendered token contract and legacy ToolSpec(...) construction
• document the supported provider shapes and export typed public helpers

Why

Equivalent function tools use different wire schemas across providers. Renderers previously handled a mixture of flat and Chat-style definitions locally, so Responses, Anthropic, and MCP inputs could be rendered inconsistently or lose schema information during parsing. Normalizing once at the boundary keeps model-specific renderers provider-agnostic and makes unsupported execution protocols fail loudly instead of being silently misrepresented.

Stack

This is stacked on #118 (codex/freeze-golden-corpus). The frozen golden corpus is unchanged by this PR.

Validation

• uv run ruff check .
• uv run ty check renderers (exit 0; existing advisory diagnostics only)
• offline suite: 130 passed
• pinned text-model suite: 2,586 passed, 110 skipped, 1 expected failure
• pinned multimodal suite: 73 passed, 17 skipped
• focused provider-shape parity: 105 passed
• normalization and actual OpenAI SDK inputs: 41 passed
• uv build

Note

Normalize provider tool specifications across all renderers

• Adds a new renderers/tools.py module that defines normalize_tool_spec() / normalize_tool_specs(), canonical types (CanonicalToolSpec, FunctionSpec, etc.), and error types (ToolSpecError, UnsupportedToolSpecError).
• Applies normalize_tool_specs() at the start of every renderer's render() method and in the _build_param_type_index / _extract_tool_names parsing helpers, replacing ad hoc envelope-unwrapping.
• Accepts tool shapes from OpenAI Chat Completions, OpenAI Responses API, Anthropic, MCP, and Pydantic-style model objects; normalizes all to a single canonical envelope.
• Risk: renderers now raise ToolSpecError or UnsupportedToolSpecError for invalid or unsupported tool protocols, where they previously silently accepted arbitrary inputs.

^{Macroscope summarized 2b19413.}