Restore fork features lost in upstream merge: shuvcode branding and subagent sidebar

[shuv1337]

Problem

A recent upstream merge unintentionally overwrote local fork features in packages/opencode/src/cli/cmd/tui/routes/session/sidebar.tsx:

1. Branding regression: The version display shows Open Code instead of shuvcode
2. Missing feature: Subagent status sidebar section (with clickable navigation) was removed

Current State

The sidebar currently shows (lines 280-284):

<span style={{ fg: theme.success }}>•</span> <b>Open</b>
<span style={{ fg: theme.text }}>
  <b>Code</b>
</span>{" "}

Expected State

Branding Fix

Should display shuvcode branding:

<span style={{ fg: theme.success }}>•</span> <b>shuv</b>
<span style={{ fg: theme.text }}>
  <b>code</b>
</span>{" "}

Subagent Sidebar Feature

Should include the subagent sidebar section that displays:

• Active/completed subagent tasks grouped by agent type
• Animated spinner for running tasks
• Clickable navigation to subagent sessions
• Status indicators (running, completed, error)

Reference Commits

These commits contain the original implementations that need to be restored:

• Branding: 6e9b984ea - "changing sidebar version display to shuvcode"
• Subagent sidebar: e768f4c19 - "feat: add subagents sidebar with clickable navigation and parent keybind"

Related upstream PR (for subagent feature context): anomalyco#4773

Acceptance Criteria

• Version display in sidebar shows shuvcode instead of Open Code
• Subagent sidebar section is restored with:
  • subagents expandable section in sidebar
  • Animated spinner for active subagent tasks
  • Clickable subagent entries that navigate to their sessions
  • Status indicators (spinner for running, ✓ for complete, ✗ for error)
• All existing sidebar functionality remains intact

Implementation Notes

Files to modify:

• packages/opencode/src/cli/cmd/tui/routes/session/sidebar.tsx:280-284 - branding fix

Key additions from subagent feature:

• Import createSignal, onCleanup from solid-js
• Import useRoute from route context
• Import ToolPart type from SDK
• Add subagents: true to expanded store
• Add spinner animation logic
• Add taskToolParts and subagentGroups memos
• Add Subagents section JSX between LSP and Todo sections

Suggested approach:

Cherry-pick or manually apply changes from commits 6e9b984ea and e768f4c19 to restore the lost functionality.