fix(web): preserve copied workspace file links

[GTC2333]

Summary

• render workspace Markdown links as stable, session-aware browser URLs that survive copying and refresh
• reopen canonical and legacy workspace file URLs in the owning session
• attach delayed directory responses to the directory that issued each request

Dependency

This is intentionally stacked on #456 so the review shows only the follow-up fixes. After #456 merges, retarget this PR to main.

Verification

• TDD regressions for copied deep links, legacy URLs, session ownership, and delayed directory responses
• npm test -w @brainpilot/web (65 files, 519 tests)
• npm run build -w @brainpilot/web
• git diff --check