Archive public-content-visibility

Final tasks ticked post-merge:
- 10.2: verified on prod that journal.routes + journal.activities still
  default to 'private' NOT NULL, with the only public rows being the
  15-each demo-bot seeded content
- 10.3: demo-activity-bot already inserts with visibility='public'
  directly in demo-bot.server.ts

Syncs the three delta specs into main:
  + activity-feed: 2 added, 1 modified
  + public-profiles: new spec (1 added)
  + route-management: 2 added, 1 modified

Moves change to openspec/changes/archive/2026-04-24-public-content-visibility.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

openspec/specs/public-profiles/spec.md

@@ -0,0 +1,26 @@
+# public-profiles Specification
+
+## Purpose
+TBD - created by archiving change public-content-visibility. Update Purpose after archive.
+## Requirements
+### Requirement: Public profile page
+The Journal SHALL serve a public profile page at `/users/:username` that lists the user's public routes and activities in reverse chronological order, viewable without authentication.
+
+#### Scenario: Logged-out visitor views a profile with public content
+- **WHEN** an unauthenticated visitor navigates to `/users/:username` for a user with at least one `public` route or activity
+- **THEN** the page renders that user's display name (falling back to username), the `@username@domain` handle, and a reverse-chronological list of their `public` routes and `public` activities
+- **AND** items marked `unlisted` or `private` do NOT appear in the list
+
+#### Scenario: Profile 404 when there is no public content
+- **WHEN** a visitor navigates to `/users/:username` for a user whose content is all `private` or `unlisted`, or for a username that does not exist
+- **THEN** the server responds with HTTP 404
+- **AND** the response does NOT distinguish the two cases, so existence of a private-only account is not leaked
+
+#### Scenario: Owner sees their own profile
+- **WHEN** a user navigates to their own `/users/:username` while logged in
+- **THEN** the page renders exactly the same as for a logged-out visitor, plus a small owner-only control strip linking to settings
+
+#### Scenario: Profile page emits social-share metadata
+- **WHEN** any visitor loads a populated `/users/:username`
+- **THEN** the page emits Open Graph tags (`og:title`, `og:site_name`, `og:type="profile"`) so links shared on social platforms render a meaningful preview
+