Fix audited reliability and release issues

[dowellhz]

Summary

• introduce content-derived document identities with legacy-state compatibility and collision protection
• fail persistence writes when required structured JSON cannot be encoded
• add localized accessibility names and remove the Apple reachability probe
• harden release temporary paths and make asset publication precede appcast exposure
• remove tracked historical installers after preserving equivalent GitHub Release assets
• add application CI, required checks, release failure-injection coverage, and repository guidance

Impact

Moved documents retain their state, replacement content cannot inherit unrelated records, failed note/word serialization preserves existing data, reader startup sends no unrelated HTTP probe, and release/appcast publication is recoverable and ordered safely.

Validation

• ./scripts/check.sh --no-build — all 156 logic tests passed
• ./scripts/check_ui_theme.sh --warnings-as-errors
• ./scripts/check_ui_accessibility.sh
• universal debug build and final arm64 debug build
• release automation dry-run failure injection
• git diff --check

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