Release v0.6.26: OpenBao settings synchronization with per-setting conflicts

README.md

@@ -383,6 +383,105 @@ This is a working native implementation, not a claim of complete UI/release pari
 The Windows focus/injection rules still apply: an unelevated process cannot edit an elevated app.
 Conversion is cancelled rather than pasting into a different window or replacing unverified recent text.
 
+## OpenBao synchronization (experimental, opt-in)
+
+The **Sync...** button is available in Settings for everyone. Synchronization remains disabled
+until you configure your own OpenBao and enable it. Connection configuration is saved separately
+in `sync.json`. The portable data directory is normally `data/` beside the executable; installations
+without a writable application directory use the existing local-app-data fallback.
+No server address or account is included in the application.
+
+The first provider is **OpenBao KV v2**. The dialog accepts an HTTPS server origin, username,
+password, KV mount (default `kswitcher`), profile path (default `personal/settings`) and userpass
+authentication mount (default `userpass`). Use the same profile on each of your PCs. This is
+administrator-provisioned private access, not public account registration. Non-root namespaces,
+reverse-proxy URL prefixes, MFA login flows and other providers are not implemented yet.
+
+Enable synchronization and choose **Save / Sign in / Sync**. The dialog saves connection changes
+immediately; the main Settings window's Save/Cancel does not control this separate configuration.
+A blank password keeps the existing Windows credential for that server, login mount and username.
+The password is saved in Windows Credential Manager, not in settings exports, logs or the remote
+profile. HTTPS certificate validation is mandatory and redirects are refused. Login tokens are
+kept in memory for one sync attempt, with best-effort self-revocation afterwards. Configure bounded
+token lifetimes on the server as well (for example a 5-minute default and 10-minute maximum).
+**Disconnect / forget password** disables synchronization and removes the current connection's
+saved credential. A request already sent to the server may still complete; its downloaded settings
+will not be applied after the connection changes. Old credentials for other connection identities
+can be removed in Windows Credential Manager under `KSwitcher.Sync/`.
+
+First connection is deliberately explicit:
+
+- **Upload local** creates the remote profile or replaces it with this PC's saved shared settings.
+- **Download remote** replaces this PC's shared settings with the server profile.
+- If both profiles are identical, ordinary Sync can establish the baseline without a replacement.
+- Unsaved edits in Settings are not synchronized. Close and reopen Settings after a download;
+  the existing stale-editor check prevents an old Settings window overwriting downloaded changes.
+
+Once connected, the resident checks at startup, every **10 minutes**, and about two seconds after saving settings, on a separate
+network thread. Errors back off for 15 minutes; the Sync button allows a manual retry. Local use
+continues offline. Independent changes to different settings fields are merged against the last
+successful baseline. **Resolve individual conflicts...** shows the name and local/server values
+for each conflict. Choose either value for selected settings and apply your choices; unselected
+conflicts stay pending. Other, nonconflicting changes continue to synchronize. Choices are checked
+against freshly read values before writing, so a stale dialog cannot overwrite a newer edit.
+Conflicting shortcuts are separate settings, including bindings for individual keyboard layouts.
+Exclusions and personal dictionary words merge by membership. Ordered layout/dictionary lists
+remain single settings because their ordering affects behavior.
+
+Snippets have persistent IDs that survive renaming. Different snippets merge independently;
+trigger and text edits within a snippet can merge too. Deleting a snippet retains a deletion
+marker, so an unchanged offline copy cannot bring it back. Deletion versus a concurrent edit
+is an explicit conflict, offering the deleted or edited version. Duplicate triggers and shortcut
+collisions created by independent edits are also presented for resolution. Deletion markers are
+retained without automatic expiry; recreating a snippet in the editor gives it a new ID.
+
+Existing profiles migrate automatically: legacy snippet IDs derive deterministically from the
+original trigger, then are stored permanently. Sync writes use envelope version 2; older clients
+refuse this version instead of dropping IDs/deletions. Update all participating PCs before using
+the new merge behavior. Existing version-1 profiles and local baselines remain readable.
+
+Download/Upload are still available for deliberate whole-profile recovery/initialization, not
+required for ordinary conflicts. Every server write uses the version just read as a CAS
+condition, including explicit Upload. A racing write is rejected rather than silently overwritten.
+Deleted server versions are not silently recreated.
+
+Hotkeys, snippets, application exclusions, layout order, conversion, screenshot and autocorrection
+preferences are shared. Startup/elevation, keep-awake, logging, history enablement/limits,
+Tesseract executable/engine selection, connection details and credentials stay local. Clipboard
+history, screenshots and dictionary files are never uploaded. Missing keyboard layouts block
+applying a remote profile until those Windows layouts are installed, preventing lost bindings.
+Settings are JSON inside OpenBao; this is not end-to-end encryption from the vault administrator.
+
+The last common profile (`sync-base.bin`) and the settings preceding the most recent downloaded
+change (`settings-before-sync.bin`) are protected with Windows DPAPI and belong to this Windows
+account/machine. Reinstallation recovery uses the remote profile and a fresh login; copying these
+local DPAPI files to a new machine does not recover them. For an older server snapshot, use OpenBao
+KV version history to restore that snapshot as the latest version, then choose Download remote.
+The app does not yet provide a server-history browser. Keep ordinary server backups too.
+
+OpenBao administrator setup:
+
+1. Enable a KV **version 2** engine at `kswitcher`; enable **Require Check-and-Set** and set
+   maximum versions to a suitable value, such as 30.
+2. Create a dedicated userpass account, with a policy restricted to the chosen profile. Do not
+   use the administrator account. For the defaults, the application needs only:
+
+   ```hcl
+   path "kswitcher/data/personal/settings" {
+     capabilities = ["create", "read", "update"]
+   }
+   path "auth/token/revoke-self" {
+     capabilities = ["update"]
+   }
+   ```
+
+3. Set bounded token lifetimes on that account/auth mount and enter its credentials in KSwitcher.
+   Keep the server's address and TLS certificate reachable/trusted on each participating PC.
+
+`SyncProvider` separates versioned read/conditional-write operations from merging, local state
+and UI integration, so another service can be added without replacing the synchronization logic.
+Protocol and conflict regressions run with `build.ps1 -Test` or CMake's `sync-regressions` test.
+
 ## Build
 
 The easiest reproducible local route uses the pinned portable w64devkit toolchain: