Drop the characters Gitea flags as ambiguous from the wiki (#416)

Gitea puts a warning box above a page that holds a character it
counts as ambiguous. Six such characters sat on four pages, so the
box showed on Concepts, Instruments, Sounds and Videos.

- Concepts: the close button is named in words, and the size reads
  320x200 px.
- Sounds: the panel size reads 560x414 px.
- Instruments: the cutoff formula uses * instead of the multiplication
  sign. This one came in with #421 after the issue was written.
- Videos: the quoted info text stops before the dash that the UI
  itself shows. Also newer than the issue.

The code is unchanged. The dash in src/editor/video/videoInfo.ts stays,
because nothing warns about it inside the canvas.

Tests:
- grep over all wiki pages for the multiplication sign, en dash,
  single right angle quote and minus sign: 0 hits, no CR.
- Rendered pages before the change: ambiguous-code-point only on
  Concepts (2), Instruments (2), Sounds (1) and Videos (1), 6 in all.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Concepts.md

@@ -372,8 +372,8 @@ one kind can be open at once — two textures, three behaviors — each with its
   tab, and the breadcrumb stays with that tab.
 - **A tab can float** (#371): right-click it and pick *Float*, and the document leaves the row for
   a window of its own above the editor. Its title bar moves the window, the lower right corner
-  sizes it, *Dock* puts the document back into the row, showing, and the `×` closes it. Only
-  documents float, never Scene or Game. A window is at least 320 × 200 px. A tab that needs more,
+  sizes it, *Dock* puts the document back into the row, showing, and the close button closes it. Only
+  documents float, never Scene or Game. A window is at least 320x200 px. A tab that needs more,
   like a Compressor's with its knobs (#378), holds its window at that size.
   - Every kind has one editor, so it has **one window**: with a texture in a window, opening
     another texture shows it there and closes the one it had. Windows of different kinds can be

Instruments.md

@@ -272,7 +272,7 @@ the volume and sweeps the filter alike. Its defaults are nodeseq's acid. Notes `
 | Input | Default | What it does |
 | --- | --- | --- |
 | **Wave** (setting) | Saw | *Saw* or *Square*, band-limited (PolyBLEP), so a high note does not alias. |
-| **Cutoff (Hz)** | 250 | Where the filter rests, 40 Hz to 18 kHz. nodeseq's Cutoff 0 to 100 is 40 Hz × 2^(8.8 × value/100), so its 30 is 250 Hz. |
+| **Cutoff (Hz)** | 250 | Where the filter rests, 40 Hz to 18 kHz. nodeseq's Cutoff 0 to 100 is 40 Hz * 2^(8.8 * value/100), so its 30 is 250 Hz. |
 | **Resonance** | 0.78 | How sharply it rings at the cutoff, 0 to 1: a Q of 0.5 dB to 17.5 dB, as nodeseq's Reso 0 to 100. |
 | **Env mod** | 0.62 | How far the envelope opens the filter: up to five octaves above the cutoff at 1, never above 18 kHz. At 0.62 that is 3.1 octaves, from 250 Hz up to 2.14 kHz. |
 | **Attack (s)** | 0.003 | How long volume and filter take to climb to the top, in a straight line. |

Sounds.md

@@ -837,7 +837,7 @@ Both (#326) work on the whole sound passing them: on a voice that is one sound,
   The knobs stay on the bottom line, centred. The levels fill the height above them. The curve
   is a square at their right, centred up and down. It grows with the tab from 180 to 360 px, but
   takes no more than 40 % of its width. A floated Compressor's window cannot be made smaller than
-  what shows every knob and the smallest pictures (560 × 414 px in the test browser).
+  what shows every knob and the smallest pictures (560x414 px in the test browser).
 - **The node is the device** (#379, #380): in the graph a Compressor is drawn as a brushed
   aluminium plate, 820x280 graph units, with its inputs on the left of it and its output on the
   right. The node is that large on purpose: the graph's zoom makes it smaller. Its settings and

Videos.md

@@ -23,7 +23,7 @@ Uploading the same file twice converts it once.
 **The upload is kept as it came.** **Download** in the picker and in the Video tab saves that
 file, not the MP4, under the name it was uploaded with. A video uploaded before 2026-10-12 has
 none kept, and the Video tab saves its MP4. An editor recording can be uploaded **without
-converting it** ("Not converted – Convert makes it usable"): it can be downloaded, but no project
+converting it** (its info says "Not converted"): it can be downloaded, but no project
 can wear it until **Convert** in the picker sends it to the worker.
 
 **Where it goes.** The upload is stored under the hash of its bytes in your folder, like every