feat(opencode): add grouped memory view

[Oerum]

Issue for this PR

Closes #16933

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds a /memory TUI view that lists the instruction and skill files OpenCode is actively using, grouped by source. It also adds route-scoped shortcuts to open the selected memory file or its directory without colliding with other keybinds.

How did you verify your code works?

• bun test --timeout 30000 in packages/opencode (1 existing fsmonitor suite failure in the full run; isolated fsmonitor file passes)
• bun run test in packages/app
• bun test ./src in packages/ui
• bun test ./test in packages/console/core
• bun run test:e2e:local in packages/app (107 passed, 4 skipped, 1 existing failure in e2e/projects/workspace-new-session.spec.ts)
• bun turbo typecheck via the pre-push hook

Screenshots / recordings

UI change in the TUI only; no recording attached.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR