fix(desktop): stop the e2e project reaching into renderer src

[OmarB97]

main does not typecheck. #337 asserted the context meter's tool-free round by
formatting the expected figure with the status bar's own compactNumber, which
meant importing src/lib/format from a spec:

e2e/context-meter-spawn.spec.ts(30,31): error TS6307: File 'apps/desktop/
src/lib/format.ts' is not listed within the file list of project
'apps/desktop/tsconfig.e2e.json'.

tsconfig.e2e.json carries "exclude": ["src", "electron"]. That is the
design, not an oversight — the e2e project is deliberately a separate island
from renderer source, and the two compile under different lib/DOM assumptions.
Adding the file to that project's include would fight the boundary to buy one
test a prettier assertion.

Re-implementing the formatter in the spec is the other obvious move and is
worse: compactNumber's own docstring calls itself THE compact-number
formatter and says not to hand-roll / 1000 display math elsewhere, which is
exactly what a copy in a test would be.

So the assertion compares numbers instead of labels — against the count the
mock actually served, never a literal, since the usage schedule is a function
of conversation length. The gauge renders one decimal in k, so a reading
round-trips to within half a step of the real figure; ±100 tokens covers that,
and the rounds are 3k apart, so the slack cannot let a neighbouring round pass
for the one under test.

npm run typecheck fails on main at this commit's parent and passes here,
which is the whole of the change.