Add Claude Code AI setup (#1090)

Summary:

Add CLAUDE.md for Claude Code support.

Differential Revision: D95275618

Author: yutingye

momentum/.claude/commands/momentum-build.md

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+---
+description: Build the momentum project
+---
+Build the momentum project. Auto-detects platform.
+
+Do the following:
+1. Read the build modes from `.llms/rules/overview.md` to get the correct mode for the current platform.
+2. If $ARGUMENTS is provided, treat it as a specific target name and run:
+   `buck build @BUILD_MODE //arvr/libraries/momentum:$ARGUMENTS`
+3. If no arguments, build everything:
+   `buck build @BUILD_MODE //arvr/libraries/momentum/...`
+4. Report the result (success or failure with errors).

momentum/.claude/commands/momentum-review.md

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+---
+description: Review a momentum or pymomentum diff against project rules
+---
+Review a momentum or pymomentum diff against project rules.
+
+If $ARGUMENTS is provided, treat it as a diff number (e.g., D{number}). Otherwise, review the current working directory changes.
+
+Do the following:
+
+1. **Load the diff**: Read the diff details including summary, test plan, and raw diff content.
+
+2. **Read project rules**: Read the relevant `.llms/rules/` files for the project(s) touched by the diff:
+   - `arvr/libraries/momentum/.llms/rules/overview.md` — commit format, reviewer
+   - `arvr/libraries/momentum/.llms/rules/code_style.md` — code organization, downstream deps
+   - `arvr/libraries/momentum/.llms/rules/cpp_style.md` — C++ style
+   - `arvr/libraries/momentum/.llms/rules/oss_maintenance.md` — OSS export, diff summary, banned words
+   - `arvr/libraries/pymomentum/.llms/rules/code_style.md` — pybind11 conventions (if pymomentum files touched)
+
+3. **Diff summary review**:
+   - Check that the public portion of the summary contains no internal references (team names, internal URLs, task/SEV/diff IDs, internal tools, internal file paths, project codenames). Follow the guidance in `oss_maintenance.md`.
+   - Check that internal context is behind `Internal:` on its own line.
+   - Check that the title follows the commit format in `overview.md`.
+   - Check that `Reviewers: momentum` is set.
+
+4. **Code review**:
+   - Check changed code against `cpp_style.md` (naming, docs, headers, error handling).
+   - Check that new `.cpp`/`.h` files are added to `build_variables.bzl`.
+   - Check that new classes are added to `gen_fwd_input.toml` (momentum only).
+   - Check BUCK/CMake sync if BUCK was modified.
+   - Check for banned words in the shipit config (read from `oss_maintenance.md`).
+   - If pybind11 bindings changed, check for Sphinx docstrings and stub regeneration.
+
+5. **Benchmark recommendation**: Follow `.llms/rules/benchmarking.md` to determine if the changed modules have corresponding benchmarks. If so, note which benchmarks should be run in the report.
+
+6. **Report**: Provide a structured review with findings organized by severity (must-fix, should-fix, nit). Include specific file:line references and benchmark recommendations if applicable.

momentum/.claude/commands/momentum-test.md

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+---
+description: Run momentum tests
+---
+Run momentum tests. Auto-detects platform.
+
+Do the following:
+1. Read the build modes from `.llms/rules/overview.md` to get the correct mode for the current platform.
+2. If $ARGUMENTS is provided, treat it as a specific test target and run:
+   `buck test @BUILD_MODE //arvr/libraries/momentum:$ARGUMENTS`
+3. If no arguments, run all tests:
+   `buck test @BUILD_MODE //arvr/libraries/momentum/...`
+4. Report the result (pass/fail counts, any failures with details).

momentum/.claude/commands/momentum-verify.md

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+---
+description: Full pre-diff verification for momentum
+---
+Full pre-diff verification for momentum. Runs build, tests, and checks.
+
+Do the following steps in order. Stop and report at the first failure.
+
+1. **Read build modes**: Read `.llms/rules/overview.md` to get the correct build mode for the current platform.
+
+2. **Build**: Build all of momentum using the platform-appropriate mode:
+   `buck build @BUILD_MODE //arvr/libraries/momentum/...`
+
+3. **Test**: Run all momentum tests:
+   `buck test @BUILD_MODE //arvr/libraries/momentum/...`
+
+4. **Downstream dependency check**: Follow the downstream dependency testing procedure in `.llms/rules/code_style.md`. Build and test the most obvious direct dependents.
+
+5. **Build file check**: Follow the code organization rules in `.llms/rules/code_style.md` to verify that any new files or classes have been registered in the appropriate build files.
+
+6. **BUCK/CMake sync check**: Follow the BUCK/CMake sync rule in `.llms/rules/code_style.md` to verify that dependency changes are reflected in both build systems.
+
+7. **OSS checks**: Follow the rules in `.llms/rules/oss_maintenance.md`:
+   - Check for banned words in changed files and the diff summary.
+   - Check that the public portion of the diff summary contains no internal URLs, SEV references, customer names, or internal team names. Remind the user to use the `Internal:` section for internal-only context.
+   - If changes affect public API surface, module structure, or documentation, check whether `__github__/README.md` or `__github__/CLAUDE.md` needs updating.
+
+8. **Doc sync check**: Follow the rules in `.llms/rules/ai_config_maintenance.md`:
+   - If directories were added/removed/renamed, check that `.llms/rules/overview.md` structure tree is up to date.
+   - If core modules were added/removed, check that `README.md` module list is up to date.
+
+9. **Benchmarks**: Follow `.llms/rules/benchmarking.md` to determine if benchmarks should be run based on which modules were changed. Run the relevant benchmarks and report results.
+
+10. **Lint**: Run `arc lint -a` on all changed files (by path, not by revision — so they get fully linted). Then run `arc lint -e extra` for comprehensive slower linters (CLANGTIDY, etc.). This runs last because earlier steps may modify code.
+
+11. **Report**: Summarize all results (build, test, downstream deps, file checks, OSS checks, doc sync, benchmarks, lint).