chats viewer always shows 0 messages — generationSpan missing input/output

[kenibarwick]

Bug

npm run chats -- --view=N and chats-tui.ts always show 0 messages for every conversation, even successful ones. The summary list works (it reads from trace metadata), but the full conversation view is broken.

Root cause

In api/chat.js, the generationSpan is ended without logging input or output:

generationSpan?.end({
  metadata: { outputTokens, inputTokens, latencyMs, cost },
})

chats.ts reads conversation content from trace.observations[0].input and trace.observations[0].output, but these are never written, so observations are always empty.

Fix

Add input and output to all three generationSpan?.end() calls (precomputed path, streaming path, and error path):

generationSpan?.end({
  input: messages,
  output: fullOutput,
  metadata: { ... },
})

For the error path, use output: fullOutput || null since the output may be partial or empty.

Impact

The full conversation viewer (--view=N, TUI) is non-functional for all conversations. Only the one-line summary preview works.