chore: switch from develop/dev to main/latest image tags

Remove develop branch references from CI, compose, env, and docs
now that all development uses trunk-based workflow on main.

- CI: remove develop branch filters and dev tag logic
- Compose: default IMAGE_TAG from dev to latest
- Env: update IMAGE_TAG default and comments
- Docs: update branching strategy, PR targets, and image tag docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -232,7 +232,7 @@ docker compose -f docker-compose.openbao.yml up -d
 sleep 30  # Wait for auto-initialization
 
 # 5. Deploy swarm stack
-IMAGE_TAG=dev ./scripts/deploy-swarm.sh mosaic
+IMAGE_TAG=latest ./scripts/deploy-swarm.sh mosaic
 
 # 6. Check deployment status
 docker stack services mosaic
@@ -526,10 +526,9 @@ KNOWLEDGE_CACHE_TTL=300  # 5 minutes
 
 ### Branch Strategy
 
-- `main` — Stable releases only
-- `develop` — Active development (default working branch)
-- `feature/*` — Feature branches from develop
-- `fix/*` — Bug fix branches
+- `main` — Trunk branch (all development merges here)
+- `feature/*` — Feature branches from main
+- `fix/*` — Bug fix branches from main
 
 ### Running Locally
 
@@ -739,7 +738,7 @@ See [Type Sharing Strategy](docs/2-development/3-type-sharing/1-strategy.md) for
 4. Run tests: `pnpm test`
 5. Build: `pnpm build`
 6. Commit with conventional format: `feat(#issue): Description`
-7. Push and create a pull request to `develop`
+7. Push and create a pull request to `main`
 
 ### Commit Format