Command Execution API Redesign (#24)

* Initial planning

* Core API implementation

* Container implementation

* Update progress in plan

* Update example to test all features

* Use simpler API for kicking off commands

* Plan to refactor the frontend

* Plan to fix streaming

* Fix process log streaming

* Clean up example

* Plan to fix port forwarding

* Fix port forwarding picking up wrong port

* Move back to subdomain routing for preview URLs

* Track port forwarding changes

* Add basic validations

* Fix ping

* Fix table styling

* Expose utils to work with SSE streams

* Cleanup WIP docs

* Fix duplicate messages in commands tab

* Refactor container handlers into separate files

* Package container code properly

* Fix execStream and cleanup legacy exec

* Purge unused streaming methods

* Showcase file & git operations via example

* Simplify command parsing & remove sandbox user

* Fix broken sse parsing due to incorrect newline

* Fix lint errors

* Replace math.random with crypto

* Add changeset

Author: ghostwriternr

.changeset/little-snails-act.md

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+"@cloudflare/sandbox": minor
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+Redesign command execution API