Show proposal identity in wizard header

[Cyber-preacher]

Summary

• replace the generic Proposal Wizard heading and instructional copy with the live proposal title and summary
• show Not set independently when either field is empty or whitespace-only
• keep long proposal identity text contained and wrapping safely beside wizard actions
• update browser and UI-contract coverage for blank, typed, hydrated, and session-switched drafts

Why

The wizard header used generic internal guidance where users need the identity of the proposal they are editing. Showing the actual title and summary keeps the current draft recognizable throughout authoring and makes missing identity fields explicit.

Validation

• yarn test (43 files, 184 tests)
• yarn typecheck
• yarn build
• focused Playwright journeys for fresh entry, live updates, hydration, browser history, and save/session switching
• complete Playwright run before locator tightening: 40 passed, with three expected strict-locator ambiguities caused by the new duplicate title display; all three corrected journeys then passed
• Prettier and git diff --check

Scope

Only the shared wizard header, its caller, layout rules, and regression tests are included. Local .codex and dummy preview files are not part of the commit.