Add triage tests, prepare-export, and UI fixes for Levkin migration.

Cherry-pick heuristics, manifest merge, global file search, scrollbar styling, and pytest/Playwright coverage unblock review and filtered export for mmetl.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help review hydrate preset-skips
+.PHONY: help review hydrate preset-skips test test-unit test-e2e fixture
 
 help: ## Show targets
 	@grep -E '^[a-zA-Z0-9_-]+:.*##' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*## "}; {printf "  \033[36m%-16s\033[0m %s\n", $$1, $$2}'
@@ -13,3 +13,36 @@ hydrate: ## Download attachments from official Slack export URLs
 
 preset-skips: ## Apply presets/levkin-skips.json channel skips to manifest.json
 	@python3 scripts/preset-skips.py
+
+cherry-pick: ## Reset picks and re-run scripts/auto-cherry-pick.py
+	@python3 scripts/auto-cherry-pick.py
+
+prepare-export: ## Build prepared-export/ from manifest.json
+	@python3 scripts/prepare-export.py
+
+fixture: ## Build tests/fixtures/mini-export from your Slack export
+	@python3 scripts/build-test-fixture.py
+
+test: test-unit test-e2e ## Run 100+ pytest + Playwright tests
+
+test-unit: fixture ## Pytest (export, cherry-pick, API)
+	@test -d .venv || python3 -m venv .venv
+	@.venv/bin/pip install -q -r requirements-dev.txt
+	@.venv/bin/python -m pytest tests/ -v --ignore=tests/e2e --cov --cov-report=term-missing:skip-covered
+
+test-cov: test-unit ## Alias with coverage report
+
+test-e2e: fixture ## Playwright UI tests
+	@npm install --no-save 2>/dev/null || npm install
+	@npx playwright install chromium
+	@SLACK_IMPORT_PORT=18765 npm run test:e2e
+
+test-e2e-headed: fixture ## Playwright with visible browser
+	@npm install --no-save 2>/dev/null || npm install
+	@npx playwright install chromium
+	@SLACK_IMPORT_PORT=18765 npx playwright test --headed
+
+test-e2e-ui: fixture ## Playwright interactive UI runner
+	@npm install --no-save 2>/dev/null || npm install
+	@npx playwright install chromium
+	@SLACK_IMPORT_PORT=18765 npx playwright test --ui