Fix snapshot and completion-wait races and stabilize native builds

[terrorproforma]

Directory timestamps can stay unchanged during a file change, and an operation can complete while an asynchronous status read is still returning old state. Verify directory membership as well as metadata, and register completion listeners before reading state so these cases are detected reliably.

• Retain transient SHA-256 digests of sorted directory entry names and compare them after traversal. Unchanged trees retain their version 1 snapshot schema and digests; validation adds one enumeration per directory.
• Close the read-before-listener gap in operation waits, preserve cancellation during the read, and return current authorized progress after timeout. Failure diagnostics capture fresh state without increasing the existing timeout.
• Make native builds reproducible with scoped LF attributes and the shared Go 1.25.12 toolchain. Failed MCP publication preserves the previous executable and removes the staged candidate.

Also update Pages configure/upload/deploy actions to their maintained Node 24 releases: configure-pages v6, upload-pages-artifact v5, and deploy-pages v5.0.1.

Validation: backend follow-up 16/16 and operation-wait 3/3 each pass across ten repeated runs; integrity/recovery 20/20, MCP lifecycle 18/18, policy 16/16, native helper 9/9 and both Go suites pass. Real Electron operation waits pass repeatedly with the original 30-second timeout. Independent review verifies snapshot compatibility and cancellation. Fresh Windows checkout, repeated build, and workspace build produce identical native hashes; an isolated file-lock test verifies failed-publication cleanup. The final Windows package passes terminal (13), filesystem helper (8), MCP contract/binary, MCPB, real operation-wait and desktop-session checks. Windows CI passed on the final PR revision before merge.