refactor(fspy): own macOS shared-memory mapping

[wan9chi]

Motivation

Replace the last shared_memory backend and remove the dependency from the workspace.

Changes

• Implements macOS shared memory with POSIX shm_open and memmap2.
• Uses the full POSIX object name as the identifier passed to open.
• Derives the mapping length from the opened POSIX object.
• Generates names from URL-safe UUIDs and retries name collisions.
• Unlinks the name when the owner is dropped or creation fails.
• Keeps existing views valid after unlink while rejecting later opens.
• Removes shared_memory and its unused transitive dependencies.

[wan9chi]

• refactor(fspy): own macOS shared-memory mapping #526 👈 (View in Graphite)
• perf(fspy): use sparse Windows shared memory #524 : 1 other dependent PR (#525 )
• fix(fspy): use memfd for Linux shared memory #523
• test(e2e): reproduce constrained dev shm failure #522
• docs(fspy): document shared-memory facade ownership semantics #521
• refactor(fspy): introduce fspy_shm facade #520
• main

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[wan9chi]

Merge activity

• Jul 11, 12:52 AM UTC: @wan9chi merged this pull request with Graphite.