refactor(openai)!: normalize Responses filter names to openai_<feature>

[leseb]

Summary

Normalizes every OpenAI Responses filter to the openai_<feature> convention set by openai_mcp_dispatch, so each filter's registered name, module path, and struct agree. This is a pre-v1 rename with no compatibility aliases: config-facing filter names change (e.g. openai_responses_format → openai_format, openai_response_store → openai_store, responses_to_chat_completions → openai_responses_to_chat_completions, and the search filters become openai_file_search_dispatch / openai_web_search_dispatch), module directories and filter structs are renamed to match, and all generated docs, READMEs, example configs, and integration tests are updated accordingly. No behavior changes.

Related issue

N/A — internal naming-consistency cleanup (no tracked issue).

Validation

• Unit tests — cargo test -p praxis-ai-apis -p praxis-ai-filters (all pass)
• make build and full-workspace cargo test --no-run
• make lint (clippy, fmt, generated filter-docs, example-tests, README syncs, responses registry, inference coverage, markdown links)
• make doc

Checklist

• I reviewed every changed line and can explain the change.
• New capabilities include an example config and functional example test. — N/A (rename only; existing example tests renamed and kept green).
• User-facing behavior and generated documentation are updated.
• Performance-sensitive changes include appropriate benchmark or load-test evidence. — N/A (no behavior or perf changes).
• Commits are signed and include a Signed-off-by trailer.

Breaking changes

Filter names used in pipeline configs change (pre-v1, no aliases). Update - filter: <name> entries:

Old	New
openai_responses_format	openai_format
openai_responses_model_rewrite	openai_model_rewrite
openai_responses_validate	openai_validate
openai_responses_rehydrate	openai_rehydrate
openai_responses_compact	openai_compact
openai_responses_proxy	openai_proxy
openai_response_store	openai_store
responses_to_chat_completions	openai_responses_to_chat_completions
openai_file_search_callout	openai_file_search_dispatch
openai_web_search	openai_web_search_dispatch