feat: add OpenAI-compatible tool call contract

[Super-Sky]

Summary

• convert OpenAI-compatible function schemas and tool_choice into Athena's provider-neutral runtime contract
• capture ordered multi-round tool calls, stable IDs, correlated results, errors, and timing from the Eino graph-native loop
• expose ordered assistant/tool messages plus compatibility tool_calls and tool_results
• persist redacted call/result traces without raw arguments or tool output
• publish typed OpenAPI schemas and synchronized bilingual documentation

Scope

This PR completes the Athena-side contract in issue #8 for tools already registered in Athena.

It deliberately does not add fund-specific objects or remote business tool execution. App-owned registration, HTTP callbacks, timeout/retry, and governance execution remain issue #9.

Stack

• Base PR: feat: add app-facing agent run API #13
• Base branch: codex/app-agent-run-api-issue-7

Validation

• env -u APP_ENV go test ./...
• go test -race ./internal/runtime ./internal/server
• go vet ./internal/app ./internal/server
• go test ./internal/runtime -run '^$' -bench '^BenchmarkToolCallTranscriptRegisterAndCorrelate$' -benchmem -count=3
• PATH=$HOME/.cache/codex-runtimes/codex-primary-runtime/dependencies/node/bin:$PATH npm run build
• python3 scripts/check_no_absolute_paths.py
• local health, typed OpenAPI, and invalid-schema HTTP smoke on port 8091
• Codex in-app Browser confirmed the local Swagger UI loaded; the large Swagger DOM inspection timed out, so contract fields were verified from the live OpenAPI JSON endpoint

go vet ./internal/runtime still reports the pre-existing EinoGraphFoundation contains sync.Mutex value-copy warnings; the same warnings reproduce on the base branch.

Refs #8