Expose apply_patch for fallback model metadata

[ctkm-aelf]

Closes #60

Changed files

• codex-rs/models-manager/src/model_info.rs updates unknown/fallback model metadata so unknown slugs such as gpt-oss:20b advertise the local freeform apply_patch tool, enable parallel tool calls, and include the multi_tool_use.parallel guidance in fallback base instructions.
• codex-rs/models-manager/src/model_info_tests.rs adds a fallback metadata regression for gpt-oss:20b.
• codex-rs/core/src/tools/spec_plan_tests.rs adds a spec-planning regression that verifies fallback metadata exposes and registers model-visible apply_patch.
• codex-rs/core/tests/suite/prompt_caching.rs adds a request-body regression proving an unknown model request sends gpt-oss:20b, exposes apply_patch, preserves multi_tool_use.parallel, and serializes parallel_tool_calls: true.

Test results

• PASS: just fmt in codex-rs.
• PASS: bash -lc 'bash "$CONSENSUS_RND_RUST_GUARD" build'.
• PASS: just test -p codex-models-manager.
• PASS: just test -p codex-core fallback_model_info_exposes_apply_patch_to_model.
• PASS: just test -p codex-core fallback_model_request_exposes_apply_patch_and_parallel_tool_calls.
• PASS: just fix -p codex-models-manager.
• PASS: just fix -p codex-core.
• FAIL, unrelated guard failure: bash -lc 'bash "$CONSENSUS_RND_RUST_GUARD" test' failed twice in codex-apply-patch::all suite::scenarios::test_apply_patch_scenarios with No such file or directory (os error 2); 90/91 guard tests passed on the rerun.

Deviations

• HOST_REFACTOR_COMMENT_POLICY was unset, normalized to none; refactor self-doc comments were not added.
• HOST_WORK_LANGUAGE was unset, so the PR artifact prose is English.
• HOST_PROTO_POLICY was unset and no schema/protocol files changed, so no schema regeneration was run.
• The host test/architecture guard remained red due to the unrelated codex-apply-patch scenario fixture lookup failure outside the authorized file scope; no scope expansion was performed.

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