feat(wallet): declare control.wallet.resetCoinDb, discarding the cached coin database

[MichaelTaylor3d]

What changed

dig-app#295 (a reset-coin-db button) needs a typed way to call dig-node's already-shipped
control.wallet.resetCoinDb (dig-node PR #543 / dig-node#384). The node dispatches the raw
JSON-RPC method by string already, but this crate's ControlMethod catalog -- the single
source of truth every client and server reads -- had no entry for it, so no typed client
(dig-app, dign, the extension) could call it.

Adds ControlMethod::WalletResetCoinDb:

• category Wallet, routing Delegated (alongside every other wallet.* method)
• ordinary token tier (not master), never an open read -- it mutates local state
• WalletResetCoinDbParams { confirm: bool } (defaults false on omission, so a client that
  forgot the flag gets the same refusal as one that typed it explicitly)
• WalletResetCoinDbResult { coins_dropped: u64, staged_dropped: u64 }, matching
  dig_wallet::sage::db::ResetReport field-for-field

Extends ControlHandler's trait + its dispatch() match arm (both exhaustive over
ControlMethod, so required for the crate to compile). The mock KAT node reproduces the real
node's confirm-required refusal, so a client that forgets the flag fails its own KATs rather
than passing them.

Docs

SPEC.md and README.md both gain the method row --
the_spec_and_readme_name_every_catalogued_method enforces this and was red until both were
updated.

Tests

• 3 existing catalog-exhaustiveness tests (hardcoded expected sets, by the file's own design)
  updated to include the new method -- was RED (3 failing) before, confirmed for the right
  reason.
• 3 new tests: refuses without confirm (explicit false and omitted field, both), and the
  success path's byte-identical round trip. Verified red-for-the-right-reason by temporarily
  neutering the guard (if false && !params.confirm), watching both refusal tests fail with
  unwrap_err() on an Ok value, then reverting.
• cargo test --lib: 196 passed, 0 failed (up from 190/3-failed pre-fix).
• cargo fmt --check + cargo clippy --all-targets: clean on touched files.

Version

0.31.0 -> 0.32.0 (minor): purely additive, no existing wire shape changed.

Blast radius

Additive-only to a catalog crate with three exhaustive-match sites (routing(), category(),
dispatch()) and one exhaustiveness test file (kats.rs) plus two docs. All four were touched;
cargo build/clippy/fmt confirm nothing else references ControlMethod non-exhaustively in
this crate. Downstream (dig-node, dig-app, dign, the extension) is unaffected until each bumps
its dependency -- release-first (CLAUDE.md §4.1).

DO NOT MERGE yet

This is the release-first prerequisite for dig-app#295. Sequence: this PR merges + publishes
to crates.io first, then dig-app bumps its dig-node-control-interface dependency and builds
the reset-coin-db button against the new typed method.

Closes nothing on its own (dig-node#384 and its dig-app companion are tracked separately).