fix: letter six count lines at the widths the design gives them

[maximsan]

Follows #551, which lettered the four count lines a table happened to name. The
table was never the boundary: the design states a letter spacing at each site,
so the check is every mono count line in lib/ read against the design's own
value. Six more were taking their rung's width instead of their own.

Line	Design	Was drawn at
01 / 05 position counter, lesson and mini-game player	0.12em	0.14em
Coffee Challenges N / N	0.06em, mono, label rung	support rung, control face
A dictionary category's term count	0.06em	0.14em
CORE LESSONS COMPLETED count	0.08em	0.14em
The tree hero's count	0.1em	0.14em
NEXT · <stage>	0.1em, mono	0.14em, control face

Hazards

• Not one shared step. The six widths run 0.06em to 0.12em, and four different
  axis tokens carry them. Reading each site rather than assuming count
  is what kept the tree lines from being lettered 0.04em too tight.
• The challenge row was wrong in more than tracking: it reached its style
  through theme.textTheme, which drew the count in the control face on the
  support rung and the kicker in mono. Both now go through AppText, and the
  kicker through SmallcapsLabel like every other kicker.
• NEXT · <stage> stops being a SmallcapsLabel. The design draws it mono at
  0.1em, not by the smallcaps rule — so it keeps its own Semantics label with
  the original casing, which is what SmallcapsLabel was giving it.

On #555. It listed three leftovers and is closed as mis-filed, not closed
by this PR. Two of its three lines are fixed here. The third — the How to
play drawer's 01 02 03 — is not a line the app draws at all: those are the
drawer's instructions, not lesson steps, and #550 owns building the drawer and
now names their 0.06em in its criteria.

Checks

• flutter analyze, dart format, metrics, comment cap and changelog: clean.
  flutter test: 2,860 passing.
• Each of the six is asserted on its rendered letter spacing. Reverting all
  six fails exactly six tests, and no others.