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>

components/settings/AgentMemoryPanel.tsx

@@ -258,7 +258,7 @@ export function AgentMemoryPanel() {
           <EmptyState
             icon={Brain}
             title="Inga minnen ännu"
-            description="När du lär assistenten saker — eller när den noterar saker själv med ditt godkännande — dyker de upp här."
+            description="När du lär assistenten saker (eller när den noterar saker själv med ditt godkännande) dyker de upp här."
           />
         )}
 
@@ -286,7 +286,7 @@ export function AgentMemoryPanel() {
                             : 'text-muted-foreground hover:bg-secondary/60 hover:text-foreground'
                         }`}
                         aria-label={row.is_pinned ? 'Lossa' : 'Fäst'}
-                        title={row.is_pinned ? 'Lossa' : 'Fäst — säkerställer att minnet alltid skickas med'}
+                        title={row.is_pinned ? 'Lossa' : 'Fäst: säkerställer att minnet alltid skickas med'}
                       >
                         {row.is_pinned ? <Pin className="h-4 w-4 fill-current" /> : <PinOff className="h-4 w-4" />}
                       </button>