PINW-40: safe bidirectional Obsidian vault compatibility

[simonislee]

Summary

• adopt existing Obsidian vaults non-destructively while preserving Markdown, YAML frontmatter, wikilinks, nested folders, .obsidian, plugin state, and attachments
• add revision-checked, cross-platform atomic text writes plus conflict-safe rename/delete commands and conflict-aware editor save queues
• enable recoverable file history by default, harden history backup/restore, and document the compatibility and ownership contract
• add bidirectional smoke coverage for external Obsidian edits and LLM Wiki writes, including stale-write, symlink, rename, delete, and attachment cases

Validation

• npm run check:frontend (132 files, 1,879 tests; typecheck and production build passed)
• npm run mcp:test (22 tests passed)
• cargo +1.91.0 fmt --manifest-path src-tauri/Cargo.toml -- --check (passed)
• cargo +1.91.0 test --locked --manifest-path src-tauri/Cargo.toml (406 passed, 2 ignored)
• git diff --check (passed)

Risk and scope

• existing user-owned vault content remains opaque and is not normalized or rewritten during adoption
• checked mutations fail on stale revisions, symlinks, out-of-project paths, non-regular files, and rename destination collisions
• hostile processes running as the same OS user are outside the desktop app's security boundary; ordinary concurrent Obsidian edits are detected through revision checks

PINW-40

[simonislee]

Opened against the upstream repository by mistake; superseded by the fork-targeted PINW-40 PR.