Adds a bund of optimizations to chatdebug:
In `coderd/x/chatd/chatdebug`:
- Adds a benchmark (excluding LLM and database stuff)
- Replaces string concatenation with strings.Builder when accumulating
stream parts (~105,000ns -> ~50,00ns)
- Removes double JSON encode in RecordingTransport (114,000ns ->
64,000ns)
In `coderd/util/strings`:
- Adds a benchmark for Truncate
- Removes unnecessary allocations in Truncate (~110,000ns -> 1,550ns in
truncation case, 1 alloc -> 0 allocs in no truncation case)
> 🤖 Claude helped with this.
Previously, Anthropic's per-modality, Priority Tier, and fast-mode rate-limit headers (`Anthropic-Ratelimit-Input-Tokens-*`, `Anthropic-Ratelimit-Output-Tokens-*`, `Anthropic-Priority-Input-Tokens-*`, `Anthropic-Priority-Output-Tokens-*`, `Anthropic-Fast-Input-Tokens-*`, and `Anthropic-Fast-Output-Tokens-*`) were shown as `[REDACTED]` in the Debug panel because they contain `"token"` in the name and fell through the generic credential filter.
Add them to the allowlist in `coderd/x/chatd/chatdebug/redaction.go` alongside the existing `Anthropic-Ratelimit-Tokens-*` entries so the limits/remaining/reset values surface in the raw response view.
Cian Johnston