style: remove em/en dashes repo-wide, add CLAUDE.md rule against them (#890)

Em dashes (—) and en dashes (–) had spread across comments, docs, tests,
and a few UI strings, reading as AI-generated boilerplate rather than
house style. Replaced each with punctuation matching its context: colon
for explanatory clauses, comma for asides, plain hyphen for numeric/legal
ranges (e.g. "21-23§"), "to"/"till" for date ranges, parentheses for
paired-dash asides. messages/en.json and messages/sv.json were fixed by
hand together to keep sv/en in sync.

Left untouched where the dash is the functional subject rather than
decorative punctuation: date-range-parser.ts's separator regex,
charset-repair.ts's CP1252 byte-mapping table (and its test), the SIE
encoding mojibake docs, generic-csv.ts's minus-sign normalizer, the
agent system-prompt files that already instruct against em dashes, and
a golden iXBRL test fixture compared byte-for-byte.

Also fixes two bugs surfaced along the way: an off-by-one in
ApiKeysPanel's scope-label split (a leftover from an earlier partial
pass), and a charset-repair test that had lost the literal en-dash it
exists to verify.

Regenerated the agent atom seed migration (skills:generate) since 27
SKILL.md files changed. Added a CLAUDE.md rule against em/en dashes,
with an explicit carve-out for the functional-dash cases above.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

scripts/setup-skv-test-company.sql

@@ -2,11 +2,11 @@
 -- Skatteverket has wired for your test BankID.
 --
 -- Replace the three placeholders below before running:
---   :user_id                — auth.users.id of the dev user signed in to gnubok
+--   :user_id: auth.users.id of the dev user signed in to gnubok
 --                              (your gnubok login email's user row)
---   :org_number_10digit     — the 10-digit form of the testredovisare SKV gave you
+--   :org_number_10digit: the 10-digit form of the testredovisare SKV gave you
 --                              (e.g. if SKV says 165020000013, use 5020000013)
---   :entity_type            — 'aktiebolag' (16-prefix) or 'enskild_firma' (19/20-prefix)
+--   :entity_type: 'aktiebolag' (16-prefix) or 'enskild_firma' (19/20-prefix)
 --
 -- Run with: psql "$DATABASE_URL" -v user_id="'<uuid>'" -v org_number_10digit="'5020000013'" -v entity_type="'aktiebolag'" -f scripts/setup-skv-test-company.sql