regression(map): #1357 cluster role pills lost the count number — show letter+count not letter-only

[Kpa-clawbot]

Symptom

Operator feedback on the #1357 deploy: cluster role pills now show only the role letter (R/C/M/S/O) — the per-role count number is no longer rendered. The count is present in aria-label / title for screen readers, but a sighted operator can't see at a glance "this cluster has 60 repeaters and 30 companions."

Pre-#1357: pills showed the count number on the colored fill.
Post-#1357: pills show only the letter.

Root cause

In the #1357 fix for the WCAG 1.4.1 violation, the pill body was switched from n (count) to letter (role identity). The intent was to add the letter as the primary non-color carrier of role identity; the regression was dropping the count instead of pairing them.

public/map.js makeClusterIcon builds: <span class="mc-pill">R</span> where it used to be <span class="mc-pill">60</span>.

Fix

Pill body becomes <letter><count> (e.g. R60, C30). Letter is the WCAG carrier; count is the data. Both at 10px monospace fit in the existing pill width up to 4-digit counts.

• DOM: <span class="mc-pill">R60</span>
• aria-label="60 repeaters" (unchanged, still screen-reader friendly).
• Min-width may need a bump if 3+ digit counts overflow; verify with a synthetic 1000-node cluster scenario.

Acceptance criteria

• Every visible role pill in a cluster renders BOTH the letter and the count, concatenated (e.g. R60, C30, M5, S1, O2).
• aria-label and title on each pill remain unchanged ("N <role>s").
• All five role letters still derived from ROLE_LETTERS (no hardcoded letters in DOM build).
• Existing fix(#1356): WCAG 2.2 AA map a11y — cluster bubbles, role pills, multi-byte labels #1357 tests still pass — letter assertions remain valid because letter is still in pill body.
• New assertion: pill body matches /^[RCMSO]\d+$/ for non-zero counts.
• WCAG 1.4.3 small-text contrast still passes (dark #1a1a1a on Wong hues, unchanged).
• Visual: 3-digit count fits without overflow; 4+ digit gets handled gracefully (CSS overflow or truncation).

Out of scope

• Re-themeing the Wong palette.
• Border-style ramp on cluster bubbles (fix(#1356): WCAG 2.2 AA map a11y — cluster bubbles, role pills, multi-byte labels #1357 V1, working as designed).
• Multi-byte hash labels (fix(#1356): WCAG 2.2 AA map a11y — cluster bubbles, role pills, multi-byte labels #1357 V3, no count regression there).

Refs

• a11y(map): cluster bubbles + role pills + multi-byte hash labels encode signal by color only (WCAG 1.4.1) #1356 (parent a11y issue)
• fix(#1356): WCAG 2.2 AA map a11y — cluster bubbles, role pills, multi-byte labels #1357 (merged fix that introduced the regression)