Closes this feature request:
[https://triggerdev.featurebase.app/p/isolated-dev-sessions-for-multiple-local-trigger-dev-instances](https://triggerdev.featurebase.app/p/isolated-dev-sessions-for-multiple-local-trigger-dev-instances)
### Feature notes:
- CLI `trigger dev` works as before
- `trigger dev --branch my-branch` to create a new branch and run
against it.
- `trigger dev archive --branch my-branch` to archive (or in webapp).
- New webapp page to manage and archive dev branches, currently feature
flagged.
### Implementation details:
- No changes to data model, no backfill. `isBranchableEnvironment`
column is ignored for dev branches, we use `parentEnvironmentId IS NULL`
instead.
- `x-trigger-branch` overloaded for preview and dev branches
- New `TRIGGER_DEV_BRANCH` env var available locally.
`TRIGGER_PREVIEW_BRANCH` overloaded for child runs.
- Lots of new glue code to sanitise the branch checks.
### Rollout
- Deploy webapp/API changes (all backwards compatible)
- Manual tests on some orgs
- Deploy docs, release CLI, flip feature flag for webapp feature
### NB
- `api.v1.projects.$projectRef.environments.ts` will return
`isBranchableEnvironment: true` for all dev environments.
### Prerequisites
- [x] Typecheck will not pass until we make a new release of
`@trigger.dev/platform` and bump it here
Chris Arderne