refactor: make all scripts multi-project via env vars

Replace hardcoded harb references across the entire codebase:
- HARB_REPO_ROOT → PROJECT_REPO_ROOT (with deprecated alias)
- Derive PROJECT_NAME from CODEBERG_REPO slug
- Add PRIMARY_BRANCH (master/main), WOODPECKER_REPO_ID env vars
- Parameterize worktree prefixes, docker container names, branch refs
- Genericize agent prompts (gardener, factory supervisor)
- Update best-practices docs to use $-vars, prefix harb lessons

All project-specific values now flow from .env → lib/env.sh → scripts.
Backward-compatible: existing harb setups work without .env changes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

factory/PROMPT.md

@@ -1,6 +1,6 @@
 # Factory Supervisor
 
-You are the factory supervisor for `johba/harb`. You were called because
+You are the factory supervisor for `$CODEBERG_REPO`. You were called because
 `factory-poll.sh` detected an issue it couldn't auto-fix.
 
 ## Priority Order
@@ -34,9 +34,11 @@ source ${FACTORY_ROOT}/lib/env.sh
 This gives you:
 - `codeberg_api GET "/pulls?state=open"` — Codeberg API (uses $CODEBERG_TOKEN)
 - `wpdb -c "SELECT ..."` — Woodpecker Postgres (uses $WOODPECKER_DB_PASSWORD)
-- `woodpecker_api "/repos/2/pipelines"` — Woodpecker REST API (uses $WOODPECKER_TOKEN)
+- `woodpecker_api "/repos/$WOODPECKER_REPO_ID/pipelines"` — Woodpecker REST API (uses $WOODPECKER_TOKEN)
 - `$REVIEW_BOT_TOKEN` — for posting reviews as the review_bot account
-- `$HARB_REPO_ROOT` — path to the harb repo
+- `$PROJECT_REPO_ROOT` — path to the target project repo
+- `$PROJECT_NAME` — short project name (for worktree prefixes, container names)
+- `$PRIMARY_BRANCH` — main branch (master or main)
 - `$FACTORY_ROOT` — path to the dark-factory repo
 
 ## Escalation