Merge Ε-W2: bank export and bank import, both verbs and both panel rows

Union of two parallel tracks. Both action rows, both menu rows, both link
edges survive; the two package CLAUDE.md files now describe the post-merge
reality rather than either side's pre-merge scope.

docs/product/bank-package.md

@@ -381,7 +381,7 @@ trim, the seed is the literal `Imported bank`.
 
 **The probe.** Let `seed` be that string and `fold(x)` be `BankBook`'s own uniqueness
 key — strip leading/trailing ASCII whitespace, lower-case ASCII letters
-(`bank_book.h:252-258`). Take the **first** name in this sequence whose fold is not
+(`bank_book.h:263-269`). Take the **first** name in this sequence whose fold is not
 already carried by a bank in the destination book:
 
     seed,  seed + " 2",  seed + " 3",  seed + " 4",  …
@@ -410,7 +410,7 @@ implementations diverge:**
    `B + 1` candidates is free by pigeonhole, so no cap is needed and none should be
    added.
 4. **The fold has exactly one home.** `import_plan` must **not** re-implement
-   `nameKey` — `bank_book.h:252-258` says in as many words that a drifted second copy
+   `nameKey` — `bank_book.h:263-269` says in as many words that a drifted second copy
    would let the uniqueness invariant be violated. The probe therefore runs behind
    `BankBook`'s own folding, which means Ε-W2-T2 adds **one additive public `const`
    member** to `BankBook` (recommended: `std::string uniqueDisplayName(const
@@ -690,7 +690,7 @@ constructors.
   freshly-generated pair.
 - **Bank generation.** Import mutates bank content that live ReaSampler 9000
   instances may play, so it must `bumpBankGeneration()`
-  (`src/shell/persist/session.h:108`, whose own comment says call sites "err toward
+  (`src/shell/persist/session.h:114`, whose own comment says call sites "err toward
   bumping"). Export mutates nothing and must bump nothing, write no ext state, and
   open no undo point.
 - **Beta/stable channel isolation.** Packages are channel-**agnostic** and this is