A whole bunch of changes to snap aimed at making it more usable for humans and agents. Here's the new CLI interface:
```
node dist/main.js --help
Options:
--version Show version number [boolean]
--sync Run compiler in main thread (instead of using worker
threads or subprocesses). Defaults to false.
[boolean] [default: false]
--worker-threads Run compiler in worker threads (instead of
subprocesses). Defaults to true.
[boolean] [default: true]
--help Show help [boolean]
-w, --watch Run compiler in watch mode, re-running after changes
[boolean]
-u, --update Update fixtures [boolean]
-p, --pattern Optional glob pattern to filter fixtures (e.g.,
"error.*", "use-memo") [string]
-d, --debug Enable debug logging to print HIR for each pass[boolean]
```
Key changes:
* Added abbreviations for common arguments
* No more testfilter.txt! Filtering/debugging works more like Jest, see below.
* The `--debug` flag (`-d`) controls whether to emit debug information. In watch mode, this flag sets the initial debug value, and it can be toggled by pressing the 'd' key while watching.
* The `--pattern` flag (`-p`) sets a filter pattern. In watch mode, this flag sets the initial filter. It can be changed by pressing 'p' and typing a new pattern, or pressing 'a' to switch to running all tests.
* As before, we only actually enable debugging if debug mode is enabled _and_ there is only one test selected.
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