Reject unlisted filesystem aliases before vault mutations

(src/serviceModules/FileSystemAdapters/pathAliasGuard.ts)
- Require every existing, unindexed path component to use a name listed by its parent directory.
- Accept case-only and Unicode-normalisation differences while caching positive directory listings briefly.

(src/serviceModules/FileSystemAdapters/ObsidianStorageAdapter.ts, src/serviceModules/FileSystemAdapters/ObsidianVaultAdapter.ts)
- Apply the alias boundary before text, binary, append, directory, removal, create, modify, rename, delete, and trash operations.
- Check both the source and destination of vault renames before calling the host API.

(src/serviceModules/FileSystemAdapters/pathAliasGuard.unit.spec.ts)
- Cover directory and file aliases across every mutating adapter route with synthetic host behaviour.
- Exercise real host filesystem aliases where the platform exposes them, including new files and directories below an aliased folder.
- Preserve listed names, case-only differences, indexed paths, and new-file behaviour.

(src/serviceModules/FileSystemAdapters/ObsidianStorageAdapter.unit.spec.ts, src/serviceModules/FileSystemAdapters/ObsidianVaultAdapter.unit.spec.ts)
- Extend existing adapter fixtures with the vault-index contract used by the guard.

src/serviceModules/FileSystemAdapters/ObsidianVaultAdapter.unit.spec.ts

@@ -42,6 +42,7 @@ describe("ObsidianVaultAdapter", () => {
         const createBinary = vi.fn().mockResolvedValue({});
         const app = {
             vault: {
+                getAbstractFileByPath: () => ({}),
                 modify,
                 modifyBinary,
                 create,