## Why
Follow-up to #16379.
`codex-rs/core/src/tools/spec.rs` and the corresponding handlers still
owned several pure tool-definition helpers even though they do not need
`codex-core` runtime state. Keeping that spec-only logic in `codex-core`
keeps the crate boundary blurry and works against the guidance in
`AGENTS.md` to keep shared tooling out of `codex-core` when possible.
This change takes another step toward a dedicated `codex-tools` crate by
moving more metadata and schema-building code behind the `codex-tools`
API while leaving the actual tool execution paths in `codex-core`.
## What Changed
- Added `codex-rs/tools/src/apply_patch_tool.rs` to own
`ApplyPatchToolArgs`, the freeform/json `apply_patch` tool specs, and
the moved `tool_apply_patch.lark` grammar.
- Updated `codex-rs/tools/BUILD.bazel` so Bazel exposes the moved
grammar file to `codex-tools`.
- Moved the `request_user_input` availability and description helpers
into `codex-rs/tools/src/request_user_input_tool.rs`, with the related
unit tests moved alongside that business logic.
- Moved `request_permissions_tool_description()` into
`codex-rs/tools/src/local_tool.rs`.
- Rewired `codex-rs/core/src/tools/spec.rs`,
`codex-rs/core/src/tools/handlers/apply_patch.rs`, and
`codex-rs/core/src/tools/handlers/request_user_input.rs` to consume the
new `codex-tools` exports instead of local helper code.
- Removed the now-redundant helper implementations and tests from
`codex-core`, plus a couple of stale `client_common` re-exports that
became unused after the move.
## Testing
- `cargo test -p codex-tools`
- `cargo test -p codex-core tools::spec::tests`
- `cargo test -p codex-core tools::handlers::apply_patch::tests`
