[thekevinbot]

Fixes #1186

Test-harness fixes for Windows. No product code changes; the two packages/rust/src edits are inside #[cfg(test)] modules.

Every change is to a test that encoded a Unix assumption, not to what the test asserts:

• extensions.rs: the fixture extension path is serialized with toml::Value instead of pasted into a basic string, where D:\a\... was an invalid escape.
• persist_parsed_path_table.rs: native paths in the parser command template go through shlex::try_quote, since shlex was stripping their backslashes. set_modified now runs on a handle opened for writing, because Windows refuses it on a read-only one.
• On-file hook fixtures (cli_e2e, cli_integration, config_root_derivation, declared_table_name, from_config, repeatable_config, sdk): these computed basename and root-relative path by splitting {path} on /. On Windows the whole backslash path ended up unescaped in the JSON payload. The hooks now normalize \ to / before splitting.
• run_on_file_passes_absolute_path_for_path_placeholder writes the received {path} to a side file and compares it byte-for-byte, so the path no longer has to survive JSON. run_on_file_does_not_substitute_abspath drops its vestigial {path} argument.
• watch_scan_correctness.rs: the helper strips either the given or the canonical root (on Windows these differ: C:\Users\RUNNER~1\... vs \\?\C:\Users\runneradmin\...) and joins the relative path with /.
• parsed_vtab::run_parser_substitutes_the_absolute_path_and_the_root: the root is std::env::temp_dir() instead of /tmp, which does not exist on Windows (os error 267).

Windows failure count

Before (run 35995035941 on #1178): 99. After (run 36432881839): 63.

Every remaining failure belongs to another issue:

• Windows: root-relative paths use backslashes, breaking glob matching and path columns #1184 (backslash separators): db::tests::files_under, process_file_event_*, relative_root_canonicalizes, vtab tests, path_table_query/gitignore/globs relative paths, watch_scan_correctness dir_renamed_within_root and dir_moved_out_of_root (event file_path has backslashes), extension_resolution::select_loadable_rejects_an_ambiguous_package.
• Windows: absolute path-table names are not recognized #1185 (absolute path-table names): path_table::tests absolute/home/parent, path_table_globs absolute, path_table_cli_e2e, path_table_query absolute.
• Windows: MSYS children glob and unescape on-file argv #1191 (new, product): MSYS children glob and unescape on-file argv. Covers printf '[{}]' brace expansion and verbatim \\?\ paths reaching hooks. Thirteen tests, listed in the issue.

E2E Verification

• Ran e2e suites locally for every affected SDK
• Python SDK e2e: pass
• TypeScript SDK e2e: pass
• Rust core e2e (if applicable): affected integration targets pass locally on Linux
• packages/python/e2e-attestations/<branch>.json receipt written (just e2e-attest-python)
• packages/ts/e2e-attestations/<branch>.json receipt written (just e2e-attest-ts)
• Command(s) run: just e2e-attest-python, just e2e-attest-ts, cargo test --features cli on the touched targets, just preflight
• Result summary: all pass. The receipts exist only because the path-based gate counts #[cfg(test)] edits under packages/rust/src.

Changelog / Migrations

• skip-changelog: on a commit: test-only change
• Migration fragment not required