fix: guard trend access against eager JSX evaluation (closes #5, #6)

[zhumengzhu]

Summary

Fixes the silent sidebar unmount reported in #5 and #6.

Root cause: npm-installed plugins live under node_modules, which opencode/opentui exclude from the babel-preset-solid transform (see opencode#39986 — the transform filter has a hardcoded node_modules exclusion since OpenTUI 0.4.2). Bun then compiles the raw TSX with its generic JSX (jsxDEV), which eagerly evaluates <Show>/<For> children before the when/guard runs. With no session data yet (fresh start / pre-sync), hasTrend is false → trend is undefined → props.trend!.color throws TypeError → the per-slot <ErrorBoundary> silently unmounts the panel with no error surfaced (#5, #6).

Changes

• TuiHitRow: props.trend!.color → props.trend?.color — safe under both eager (bun generic JSX) and lazy (babel-preset-solid) evaluation
• Hardening: same-class ! usages in cache-ttl-view.tsx (elapsed()!) and main-session-view.tsx (messages!) → optional props with runtime guards
• tests/eager-render.test.ts: renders TuiHitRow with trend=undefined under bun's eager load path (verified to fail on the pre-fix !)
• tests/eager-safe-jsx.test.ts: static scan for guard-variable ! derefs and optional-chain-then-bare-deref in src tsx (8 cases)
• AGENTS.md: new Eager-safe JSX code convention
• devDep @opentui/solid 0.3.0 → 0.4.5 (opencode 1.18.x catalog version); version bump 0.6.3 → 0.6.4

Verification

• 345 tests pass / 0 fail
• Reproduced locally: same source compiled under the two load paths behaves differently — node_modules path (eager) throws props.trend.color on trend=undefined; file path (lazy) does not. The fix passes both.
• End-to-end verified on opencode 1.18.15 (npm install path): sidebar panel renders correctly after the fix.

Closes #5, #6