bug(ui): markdown heading markers (###) shown verbatim in quote chips render as cramped literal text

[cat0825]

What happened

A quote chip / file-reference strip in the chat surface shows markdown source
verbatim, including heading markers:

…/path/to/issue.md ### Description

The three # characters render as literal text at small size, and the dense
# strokes read as a cramped/overlapping blob instead of three distinct
hashes.

For reference, the same string rendered locally with the system font stack at
13pt medium is clearly spaced — the cramped look comes from displaying the
markdown marker as plain text in the chip, not from font shaping:

Root cause (verified at source level — not a markdown parse bug)

The markdown pipeline in this build (@astryxdesign/core, packaged as
markdown-body-*.js) parses ATX headings with:

let n = e.match(/^(#{1,6}) +(.*)/);
if (n) { c.push({type:'heading', level:n[1].length, children:W(n[2], o)}), l++; continue }

The regex anchors the markers at line start (^). Running the exact packaged
parse logic:

".analysis/issue-new-messages.md ### Description"  → NO MATCH → "###" kept as literal text
"### Description"                                  → MATCH   → heading level 3, markers consumed

So the renderer is correct per CommonMark: mid-line ### is not a heading
marker and is emitted as plain text. The problem is presentation-only: quoted
excerpts preserve markdown source (use-message-selection-quote.ts captures
selection.toString().replace(/\s+/g,' ').trim() verbatim), so ### can
land in a chip and render as cramped literal hashes.

Full evidence trail from the shipped build:

• 154 renderer chunks + 5 main bundles + full @astryxdesign/core source
  (1987 files): no code path emits # characters as a level badge; no
  "###" literal, no "#".repeat, no CSS content:"#...".
• Font stack is the system default (-apple-system, BlinkMacSystemFont, ...);
  no custom font-feature or negative letter-spacing involved.

Suggested fixes (any of)

1. When building a quote/chip from a markdown document, strip heading markers
   (^#{1,6} → "") so the chip shows Description instead of
   ### Description.
2. Keep the source verbatim but render literal # runs with explicit
   letter-spacing (or a code/monospace style) so three hashes never look
   merged.
3. Audit other surfaces that show markdown source as plain text (file
   reference previews, raw-source views) for the same verbatim-marker display.

Environment

• App: Maka desktop 0.1.5 (Electron, macOS Apple Silicon)
• Surface: chat / quote reference strip