Suggestions: stop re-nagging resolved edits + fix typographic anchoring

Two fixes for the "accept Petal's change, then it nags about the same
sentence moments later" report:

- replacePending now suppresses any freshly-generated suggestion whose
  original->replacement matches one the user already accepted or
  dismissed for that doc. The model has no memory between passes, so
  without this it re-proposes the identical edit on the next checkpoint.

- findRange anchored suggestions by exact string match, which missed
  whenever the model echoed an `original` with plain ASCII (straight
  quotes, --, ...) while the document held the Typography-converted
  glyphs (curly quotes, em-dash, single-char ellipsis). The miss meant
  no highlight AND a silent no-op on accept, which then fed the re-nag
  above. foldTypography canonicalizes those variants (with a source
  index map for length changes) so matching survives the mismatch.

Covered by a server-side regression test (accept+dismiss then re-check
returns nothing) and frontend unit tests for the fold and anchoring.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

web/src/components/Editor/SuggestionHighlight.test.ts

@@ -0,0 +1,54 @@
+import { describe, it, expect } from 'vitest'
+import { foldTypography, findRange } from './SuggestionHighlight'
+import { Schema, type Node as PMNode } from '@tiptap/pm/model'
+
+// A minimal doc/paragraph/text schema, enough to exercise findRange's textblock
+// walk without pulling in the full editor.
+const schema = new Schema({
+  nodes: {
+    doc: { content: 'block+' },
+    paragraph: { group: 'block', content: 'inline*', toDOM: () => ['p', 0] },
+    text: { group: 'inline' },
+  },
+})
+
+// Build a single-paragraph doc with the given plaintext.
+const para = (text: string): PMNode => schema.node('doc', null, [schema.node('paragraph', null, text ? [schema.text(text)] : [])])
+
+describe('foldTypography', () => {
+  it('folds curly quotes back to straight ASCII', () => {
+    expect(foldTypography('“He’s here,” she said').folded).toBe('"He\'s here," she said')
+  })
+
+  it('folds dashes and ellipsis, keeping a source-index map across length changes', () => {
+    const { folded, map } = foldTypography('wait—really...')
+    expect(folded).toBe('wait—really…')
+    // The em dash is already one glyph; the `...` collapsed 3 source chars to 1,
+    // so the trailing sentinel still points just past the last source char.
+    expect(map[map.length - 1]).toBe('wait—really...'.length)
+  })
+
+  it('treats `--` and `...` typed-but-unconverted as their canonical glyphs', () => {
+    expect(foldTypography('a--b...c').folded).toBe('a—b…c')
+  })
+})
+
+describe('findRange typographic anchoring', () => {
+  it('anchors a model echo with straight quotes onto curly-quote document text', () => {
+    const doc = para('She said “hello” to me')
+    const range = findRange(doc, '“hello”'.replace(/[“”]/g, '"')) // model echoed "hello"
+    expect(range).not.toBeNull()
+    // The matched span must cover the curly-quoted region in the real document.
+    expect(doc.textBetween(range!.from - 1, range!.to - 1)).toContain('hello')
+  })
+
+  it('anchors an ASCII `--` echo onto an em-dash in the document', () => {
+    const doc = para('I waited—forever')
+    const range = findRange(doc, 'waited--forever')
+    expect(range).not.toBeNull()
+  })
+
+  it('still returns null when the text genuinely is not present', () => {
+    expect(findRange(para('nothing to see'), 'absent phrase')).toBeNull()
+  })
+})