fix(tui): pass roots:true in session list bootstrap to fix child session dilution

[dinhphieu]

Issue for this PR

Closes #16270
Closes #13877

Type of change

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

What does this PR do?

The TUI session list bootstrap in sync.tsx fetches sessions without passing roots: true. This means root sessions and child sessions (forks, compaction) are mixed together. Session.list() defaults to LIMIT 100, and the TUI dialog filters client-side with .filter(x => x.parentID === undefined).

For users who spawn subagents/tasks heavily, child sessions vastly outnumber roots. In my case: top 100 by time_updated contains 95 children and only 5 roots. So /sessions shows ~5 conversations despite 584 existing in the DB.

Fix: add roots: true to the bootstrap call so the server applies WHERE parent_id IS NULL before the limit. All 100 slots go to actual conversations.

How did you verify your code works?

Verified against a production DB with 8,976 sessions (584 root, rest children):

-- Before (without roots:true): 95 children, 5 roots in top 100
SELECT CASE WHEN parent_id IS NULL THEN 'ROOT' ELSE 'CHILD' END as type, COUNT(*)
FROM (SELECT * FROM session ORDER BY time_updated DESC LIMIT 100) GROUP BY type;

-- After (with roots:true): all 100 are root sessions
SELECT COUNT(*) FROM (SELECT * FROM session WHERE parent_id IS NULL ORDER BY time_updated DESC LIMIT 100);

Screenshots / recordings

N/A — not a UI change, just a query parameter fix.

Checklist

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

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