Add frailbox buddy allocator

[jarlyn95]

Summary

Adds a frailbox buddy allocator implementation for issue #4.

/claim #4

Changes

• Added the public buddy allocator API in frailbox/include/buddy.h.
• Implemented an mmap-backed global buddy allocator in frailbox/src/buddy.c with power-of-two blocks, a 64-byte minimum block size, free-list splitting, and buddy coalescing.
• Added allocation/deallocation stats, allocated/free block counts, largest free block, and fragmentation ratio reporting.
• Added a small standalone C test for allocation, free/coalescing, oversized allocation failure, and stats behavior.
• Included the required diagnostic artifacts: diagnostic/build-00000000.logd and diagnostic/build-00000000.json.

Testing

• gcc -Wall -Wextra -Wpedantic -std=c2x -I frailbox/include frailbox/tests/test_buddy.c frailbox/src/buddy.c -o /tmp/test_buddy && /tmp/test_buddy - PASS.
• make -C frailbox - PASS. The new buddy.c compiled under the repository C flags; existing warnings remain in arena.c and logger.c.
• python3 build.py -m frailbox --verbose - PASS and generated diagnostic artifacts.
• python3 build.py - ran as requested; 8/10 modules passed, including frailbox. The full build failed in unrelated modules: market timed out downloading the Go 1.26 toolchain, and openapi-haskell failed on an existing missing liftA2 import.

Diagnostic password: 041370d59f0a326a255a

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

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• I would like to request that my diagnostic build log is removed before merging

[Copilot]

Pull request overview

Adds a new mmap-backed buddy allocator to the frailbox module, exposing a public API and providing a small standalone test plus required diagnostic artifacts for issue #4.

Changes:

• Introduces a public buddy allocator API (buddy_init, buddy_alloc, buddy_free, buddy_stats) and stats reporting.
• Implements a global buddy allocator with splitting/coalescing and fragmentation metrics.
• Adds a standalone C test that exercises allocation/free/coalescing, oversized allocation failure, and basic stats behavior.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 3 comments.

File	Description
frailbox/include/buddy.h	Declares the buddy allocator public API and the buddy_stats_t struct.
frailbox/src/buddy.c	Implements the mmap-backed buddy allocator, freelists, coalescing, and stats computation.
frailbox/tests/test_buddy.c	Adds a standalone smoke test for allocations, frees/coalescing, oversized allocations, and stats.
diagnostic/build-00000000.json	Updates diagnostic build metadata to satisfy the repository’s PR requirements.

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