A healthy forge's home and board carry no alert banner: design-lint refuses a standing alert there, and a test counts zero #10699

Intent: no red noise; a setting is one line where it belongs, never a banner over the board.

Done:

• [x] bun scripts/design-lint.ts gains a rule (name it banner) that refuses role="alert" or a full-width danger-coloured block in the home and board page builders (src/web/pages/board.ts, the home builders), with a comment-free opt-out only for a transient flash.
• [x] A test renders / and /board for an admin on a seeded healthy forge and asserts no element with role alert, and no .banner/.notice-danger class, is in the first view.
• [x] A test with one real fault (for example egress in report mode) shows the fault as one line on its own settings page and in the system card, not on / or /board.
• [x] Rule and test are documented in two lines in docs/DESIGN.md's area file, not a new component class.

Files: scripts/design-lint.ts, src/web/pages/board.ts, test/calm-banners.test.ts, docs/design/areas/. Risks: a legitimate transient flash must stay; run design-lint on the whole tree before pushing and fix what it names. Brief: a design builder (scout).

Reviewed pull #10705 at its head: ticked bun scripts/design-lint.ts gains a rule (name it banner) that refuses role="alert" or a full-width danger-coloured block in the home and board page builders (src/web/pages/board.ts, the home builders), with a comment-free opt-out only for a transient flash.; A test renders / and /board for an admin on a seeded healthy forge and asserts no element with role alert, and no .banner/.notice-danger class, is in the first view.; A test with one real fault (for example egress in report mode) shows the fault as one line on its own settings page and in the system card, not on / or /board.; Rule and test are documented in two lines in docs/DESIGN.md's area file, not a new component class..