.fab exclusion scoping: classes in the manual export (Task 4, v0.136.0)

SQ6 over-capture FIXED for classified apps: the userdata root tar is exclude-scoped (keeps only
ancestors/descendants of a SELECTED bind relpath — R1-C, the tier2Reconcile keep-rule); no selected
userdata bind → no root tar (radarr state-only). New appbackup.ComputeFabBuckets (shared
resolveGuardCollapse pipeline; class buckets; guards over ALL classes; no cross-bucket containment).
appexport/fabplan.go: computeFabPlan + tarDirectoryExcluding + fabEstimateSplit. ExportRequest gains
DeselectOptional/OptInExcluded (both start handlers — two-call-site); mandatory is a server-side
floor. Manifest v1 + import UNTOUCHED; legacy apps byte-identical to v0.130.0. Estimate additive
class split; export UI: locked-mandatory/optional-checkboxes/excluded-opt-in + two-number warning.
All 6 §10 red-proofs verified. 6D Accept #1 now runs against this shape.

controller/README.md

@@ -382,6 +382,8 @@ Per-app export creates a self-contained `.fab` file (tar.gz, optionally encrypte
 
 **Mount discovery (v0.130.0, C6B-F1):** `stacks.ExportDataMounts` — the `${HDD_PATH}` binds unioned with the `${USERDATA_PATH}` **root** (single `userdata` entry) when the compose uses the standard userdata convention; pre-fix the adapter was `${HDD_PATH}`-only, so 12/13 `needs_hdd` catalog apps exported hollow (config-only) bundles. The root (not per-bind) keying is what round-trips through the import's basename→`<HDD_PATH>/<subdir>` mapping. A basename collision between mounts fails the export loudly. The share-removal endpoint also refuses while a deployed app's HDD_PATH is on the share (C6B-F2 guard).
 
+**Class-scoped export (v0.136.0, Task 4 — the SQ6 fix):** for a **classified** app the userdata root tar is **exclude-scoped** — it keeps only dirs that are an ancestor-or-descendant of a SELECTED bind relpath (mandatory ∪ checked-optional ∪ opted-in-excluded; R1-C, the `tier2Reconcile` keep-rule), so sibling apps' content no longer rides along. No selected userdata bind ⇒ the root tar is **skipped entirely** (radarr → state-only). Non-selected HDD bind mounts are skipped; a mount matching no classified bind is kept (fail toward capture). Mechanics unchanged: **ONE** userdata tar, per-mount skip, **manifest v1 + import untouched**. The plan is pure (`appexport/fabplan.go` `computeFabPlan` over `appbackup.ComputeFabBuckets`); `tarDirectoryExcluding` prunes excluded subtrees in the walk. **Legacy (no-block) apps export byte-identically to v0.130.0.** Mandatory paths are a **server-side floor** (a client cannot deselect them). The export page shows the class selection UI (locked mandatory, pre-selected optional checkboxes, opt-in excluded behind the two-number warning + FileBrowser pointer); the estimate carries an additive class split (`ExportEstimate.MandatoryItems/OptionalItems/ExcludedItems` + `BaseBytes`).
+
 **Import flow:** Decrypt if needed → extract → **validate-before-destroy** (v0.125.0: every manifest-claimed data tar must be present non-empty BEFORE the app is stopped or any volume removed — hollow bundles from containerized ≤0.124.0 exporters are refused with the app untouched) → prepare stack dir (create new or `compose down --volumes` for existing) → restore config (re-encrypt app.yaml with current server key) → restore user data (HDD tars; volumes populate via `docker cp` streaming) → restore DB (start DB service, wait for ready, import dump) → start full stack → refresh UI.
 
 **Architecture:** `internal/appexport/` package with `ExportStackProvider` adapter interface (same pattern as `backup.StackDataProvider`). `exportAdapter` in `main.go` bridges `stacks.Manager` to the provider.