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>

app/api/export/articles/route.ts

@@ -9,7 +9,7 @@ import type { Article } from '@/types'
 /**
  * GET /api/export/articles[?format=csv][&include_inactive=1]
  *
- * Downloads the article register as xlsx (default) or csv. Read-only — viewers
+ * Downloads the article register as xlsx (default) or csv. Read-only: viewers
  * may export. Column headers match the article importer's detector keywords so
  * the file round-trips (export → edit → re-import).
  */

app/api/export/customers/route.ts

@@ -9,7 +9,7 @@ import type { Customer } from '@/types'
 /**
  * GET /api/export/customers[?format=csv]
  *
- * Downloads the customer register as xlsx (default) or csv. Read-only — viewers
+ * Downloads the customer register as xlsx (default) or csv. Read-only: viewers
  * may export. Headers match the customer importer's detector keywords so files
  * round-trip.
  */

app/api/export/suppliers/route.ts

@@ -9,7 +9,7 @@ import type { Supplier } from '@/types'
 /**
  * GET /api/export/suppliers[?format=csv]
  *
- * Downloads the supplier register as xlsx (default) or csv. Read-only — viewers
+ * Downloads the supplier register as xlsx (default) or csv. Read-only: viewers
  * may export. Headers match the supplier importer's detector keywords so files
  * round-trip.
  */