fix(fs): normalize VFS paths in HostMounts to prevent host traversal

[chaliy]

Motivation

• The host-path resolver could preserve ./.. in the suffix returned by strip_prefix, allowing a VFS path like /workspace/../secrets to map to a host path that the OS resolves outside the intended mount.
• Normalize mount points and lookup paths with the VFS normalizer so the resolver matches the VFS meaning, not the raw spelling, preventing host traversal mismatches.

Description

• Normalize recorded mount points in HostMounts::new by applying normalize_path to each HostMount.vfs_path.
• Normalize incoming lookups in HostMounts::resolve by calling normalize_path on the vfs_path before prefix matching and joining.
• Add regression tests parent_components_are_normalized_before_mount_selection and mount_points_are_normalized_when_the_table_is_built in crates/bashkit/tests/integration/host_mounts_tests.rs.
• Document the invariant and add threat-model entry TM-ESC-034 in knowledge/foundations/vfs.md and knowledge/security/threat-model.md explaining that mounts and lookups are normalized before matching.

Testing

• cargo test --features realfs -p bashkit --test integration host_mounts_tests passed (13 tests).
• cargo fmt --check passed.
• cargo clippy --features realfs -p bashkit --test integration -- -D warnings passed.
• just check-okf ran and reported OKF v0.2 conformance (no failures reported).

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	bashkit	442cd8a	Commit Preview URL	Aug 07 2026, 09:37 AM