gui: spec-blind suite; search finds the best match, axis ticks never overflow

tests/spec_gui.rs (31 spec-blind tests): exact money text round-trips,
file names never escape the folder or hit a Windows device name, history
against a browser model, fuzzy search against a subsequence model, axis
ticks, the view model against ledger-core, and the attention list.

Found and fixed:
- fuzzy matched greedily, so "ac c" scored 1 for "c" (the "c" inside
  "ac") instead of 5 for the word "c"; it now scores the best alignment.
- ticks accumulated float error (a last tick at -5.55e-17 for a top of
  0), gave more than n + 2 ticks at large magnitudes with tiny spans,
  and overflowed for spans near f64's limit. Ticks are now whole
  multiples of the step, checked, with [lo, hi] when f64 has no nice step.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX

Cargo.lock

@@ -3631,6 +3631,7 @@ dependencies = [
  "ledger-import",
  "ledger-store",
  "notify",
+ "proptest",
  "rust_decimal",
  "serde",
  "serde_json",