[bitborne]

Description

Move the startup-only MC_STORE_PIN_MEMORY_MAX_BYTES setting out of the
registered pinned-memory manager and into a dedicated
RegisteredPinnedMemoryConfig.

• define the environment variable in the common grouped catalog;
• preserve the existing unset, empty, zero, valid, invalid, and diagnostic
  behavior;
• make the manager consume the parsed configuration instead of reading and
  parsing the environment itself.

Module

• Transfer Engine (mooncake-transfer-engine)
• Mooncake Store (mooncake-store)
• Reshard (mooncake-reshard)
• Mooncake EP (mooncake-ep)
• Mooncake PG (mooncake-pg)
• Integration (mooncake-integration)
• P2P Store (mooncake-p2p-store)
• Python Wheel (mooncake-wheel)
• Common (mooncake-common)
• Mooncake RL (mooncake-rl)
• CI/CD
• Docs
• Other

Type of Change

• Bug fix
• New feature
• Refactor
• Breaking change
• Documentation update
• Performance improvement
• Other

How Has This Been Tested?

Test commands:

cmake --build build --target registered_pinned_memory_test -j32
ctest --test-dir build -R '^registered_pinned_memory_test$' --output-on-failure
pre-commit run --files \
  mooncake-common/include/environment_variables.h \
  mooncake-store/src/config/registered_pinned_memory_config.h \
  mooncake-store/src/config/registered_pinned_memory_config.cpp \
  mooncake-store/src/registered_pinned_memory.h \
  mooncake-store/src/registered_pinned_memory.cpp \
  mooncake-store/src/CMakeLists.txt \
  mooncake-store/tests/registered_pinned_memory_test.cpp

Test results:

• Unit tests pass
• Integration tests pass (if applicable)
• Manual testing done (describe below)

Checklist

• I have performed a self-review of my own code
• I have formatted my code using ./scripts/code_format.sh
• I have run pre-commit on the files changed in this PR and all hooks pass
• I have updated the documentation (if applicable)
• I have added tests to prove my changes are effective
• For changes >500 LOC: I have filed an RFC issue

AI Assistance Disclosure

• No AI tools were used
• AI tools were used (specify below)

Codex helped trace the existing environment semantics, implement the refactor,
add focused tests, and run formatting and review checks. I reviewed the
changes and test results.

[Aionw]

LGTM