Implement file-backed repositories via .store files

[KrisSimon]

Migrated from GitLab MR !223 (open)
feature/store-files-178 → main
Originally created: 2026-04-02
Author: Kris Simon
Labels: 0.9

Summary

Implements #178 — file-backed repositories via .store files.

• .store files are YAML files that automatically seed repositories at startup
• File permissions control writability: chmod o+w enables write-back
• Write-back uses debounced (1s) atomic writes via temp file + rename
• aro build rejects writable stores (can't write back into a binary)

Changes

• Sources/ARORuntime/Store/StoreFileLoader.swift — Discovers and parses .store files
• Sources/ARORuntime/Store/StoreFlushService.swift — Actor-based write-back with debounce
• Sources/ARORuntime/Application/Application.swift — Seeds repositories before Application-Start, flush on shutdown
• Sources/ARORuntime/FileSystem/FormatDeserializer.swift — Fix YAML array parser for multi-line objects
• Sources/AROCLI/Commands/RunCommand.swift — Verbose logging for store files
• Sources/AROCLI/Commands/BuildCommand.swift — Reject writable stores at build time
• Examples/StoreFileDemo/ — Example with read-only product catalog
• Tests/AROuntimeTests/StoreFileTests.swift — 19 tests (loader, flush, integration)
• Proposals/ARO-0073-store-files.md — Formal proposal
• Book/TheLanguageGuide/Chapter36-Repositories.md — Store files section added
• Wiki — New Guide-Store-Files page, updated Guide-Repositories and sidebar

Test plan

• swift build passes
• swift test --filter StoreFile — 19/19 tests pass
• swift test --filter RepositoryStorage — no regression (19/19 pass)
• swift test --filter FormatSerializer — no regression (23/23 pass)
• swift run aro run ./Examples/StoreFileDemo — output matches expected.txt
• Integration test suite (perl t/run_tests.pl)

Closes #178