fix(desktop): normalize agent pubkeys through one helper, and guard it

[mfethe1]

fix(desktop): normalize agent pubkeys through one helper, and guard it

normalizePubkey is trim().toLowerCase(). Across features/agents, 20 call
sites reached for a bare .toLowerCase() instead. The two agree for every
well-formed pubkey and disagree the moment one carries surrounding whitespace,
so the divergence is invisible until a value arrives from somewhere untidy — a
pasted allowlist entry, a relay tag, a config file — and then one surface stops
matching another with nothing thrown and nothing logged.

That is the same failure shape the agent-identity work keeps turning up: two
places answer "is this the same agent?" differently, and a user reports that an
agent "isn't there".

One site was already asymmetric rather than merely inconsistent.
RespondToField.handleRemove compared p.toLowerCase() against a pubkey that
had been normalized, so removing an allowlist entry could fail to match the
entry it was given. That is a live bug, not a style point.

Guard

check-pubkey-normalization.mjs matches any .toLowerCase() call and then
filters on the receiver, rather than anchoring the pubkey inside the pattern.
The first version did anchor it, and could not see
agent?.pubkey.toLowerCase() — the optional link sits between the identifier
and the segment being matched. Filtering on the receiver found three
optional-chained sites the initial sweep had skipped, two of which the anchored
pattern could never have reported.

Scoped to src/features/agents deliberately. Hand-rolled lowercasing is
repo-wide — 87 files under desktop/src against 113 using normalizePubkey —
and failing on all of them would make the guard unshippable. A guard that must
be disabled to land anything protects nothing. So it covers the surface whose
divergence caused an outage, and covers it completely: no allowlist. Widening it
is a follow-up that has to arrive with the call-site fixes, not a flag flip.

Interaction with #6077

Both this PR and #6077 add a check:* script and extend the same check line
in desktop/package.json, so whichever lands second needs a one-line rebase
there. Nothing else overlaps: #6077 guards how an identity KEY is minted, this
guards how the pubkey inside it is normalized.

Note that main recently removed pnpm check:file-sizes from that line (#6187
made the ratchet a first-class root gate). Neither PR should put it back.

Verification

npx tsc --noEmit clean. pnpm check clean. Desktop unit suite: 4993 passed,
0 failed.

Guard proven to fail, not just to pass: an injected x.pubkey.toLowerCase()
under features/agents is reported and exits 1; removing it exits 0.

Signed-off-by: Michael Feth michael@jira-flow.com