[JetSquirrel]

Problem

On Windows, creating or writing to a graph anywhere under C:\Users\... fails:

storage error: open namespace directory '\?\C:\Users': Access is denied. (os error 5)

HawDB flushes every parent folder up to the drive root when it opens a graph for writing, and an ordinary user can't open C:\Users for writing. A machine with only drive C had nowhere obvious to put a graph.

This isn't waiting on HawDB. nowledge-co/hawdb#1255 tracks it, and our pinned 0.24.0 already has the option for it, DatabaseConfig::namespace_durability_anchor. We never set it.

Change

• On Windows, a graph inside the home folder now uses that folder as its anchor. HawDB still flushes everything from the graph up to and including the home folder.
• Paths outside the home folder and other platforms keep the full walk. C:\graphs still fails, with a reworded hint.
• The anchor depends only on the graph's path, so the CLI and the window always agree, which HawDB requires.
• The README and the comment in .cargo/config.toml now say the same.

The decision to review

Setting an anchor means we promise the home folder is already durable; HawDB doesn't check. HawDB's namespace durability doc describes this pattern for the OS-provisioned LocalAppData folder and says not to do it for a folder the app just created. The home folder is also provisioned by Windows, but the doc doesn't name it, so this is our reading of it.

Not tested: power loss. HawDB's doc also lists Windows namespace power-loss qualification as still open, with or without an anchor.

Testing

On Windows 11 as a non-admin user:

Graph location	Create	Write, then read back
Inside the home folder	Works	Works, including read-only
Same, typed in lower case (c:/users/...)	Works	Works, including read-only
C:\ProgramData\... (outside home)	Fails with the new hint, leaves nothing behind	Not applicable
E:\...	Works	Works, including read-only

• New test a_graph_in_the_home_folder_can_be_created_and_reopened fails with os error 5 when the anchor is turned off. It returns early if the temp folder isn't under the home folder, so it may not exercise this on every CI machine.
• cargo test --workspace and cargo clippy --workspace --all-targets -- -D warnings pass locally.
• Not run in the window; it opens graphs through the same open_inner.

After this and #57 both merge

This is based on main, so it can't touch text that only exists in #57. That text needs a small follow-up:

• The probe_location comment in location.rs, which says HawDB needs write access to every parent folder.
• The graph_dialog.new.no_suggestion string, which says graphs may not work on drive C.

suggest_location needs no change: its probe will now succeed for Documents.

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