Argument/flag validation failures in the minimal CLI framework threw a
plain Error that bubbled to the process-level catch in cli.ts, which
dumps a Bun.inspect code frame — a minified dist/cli.js excerpt in
compiled binaries. A missing model on `omp bench` looked like a crash.
- Add CliUsageError; throw it from Command.parse for missing/invalid
args and flags.
- Catch CliUsageError in run(): print `error: <msg>` plus the command
usage line to stderr, exit 1, no stack.
- Render required variadic positionals as MODELS... in usage, not the
misleading optional [MODELS]; extract commandUsageLine helper.
Fixes#5369
- Fixed help rendering so `--help` no longer triggers unrelated command loaders.
- Fixed startup span logging to emit markers only with PI_DEBUG_STARTUP set.
- Fixed logger startup trace behavior for `:start`, `:done`, and `:fail` phases.
- Fixed prompt template processing with cached raw-template compilation and safer formatting.
- Optimized symbol and tag parsing in prompt templates via manual parsers.
Brent