feat(workflows): wire TaskUnit/Orchestrator activities, add k8s deploy manifests

Implements real activity-calling logic in OrchestratorWorkflow and
TaskUnitWorkflow (previously stubs), adds GitDiffActivity, and expands
PlanningActivity's I/O to carry repo path and prior task results.

Adds k8s/ deployment manifests (worker Deployment, orchestrator Job,
Kustomize base) for the poimen-workflows Temporal worker, using a
dedicated Kubernetes namespace `poimen` and Temporal namespace
`poimen-harness` rather than sharing the Temporal server's own
`temporal`/`production` namespaces.

tests/e2e_setup.sh

@@ -0,0 +1,62 @@
+#!/bin/bash
+
+# E2E Test Setup for T0.9
+# Creates a fixture repository for testing the full orchestrator workflow
+
+set -e
+
+FIXTURE_DIR="${1:-/tmp/fixture}"
+REMOTE_DIR="${2:-/tmp/fixture-remote}"
+
+echo "=== Creating fixture repository structure ==="
+mkdir -p "$FIXTURE_DIR"/tasks/.orchestrator/lessons
+mkdir -p "$REMOTE_DIR"
+
+# Initialize the fixture repo as a git repo
+cd "$FIXTURE_DIR"
+git init
+git config user.email "[email protected]"
+git config user.name "Test User"
+
+# Create tasks/INDEX.md
+cat > tasks/INDEX.md << 'EOF'
+# Fixture Task Board
+
+This is a simple fixture repository for testing the Poimen Orchestrator system.
+
+## Tasks
+
+| ID | Description | Status |
+|----|-------------|--------|
+| T0.1 | Create output.txt with "hello world" | [ ] |
+| T0.2 | Create result.json with valid JSON | [ ] |
+| T0.3 | Create done.txt with "COMPLETE" | [ ] |
+EOF
+
+# Create tasks/board.md
+cat > tasks/board.md << 'EOF'
+# Task Board — Fixture T0
+
+| ID | Scope | Status | Branch | Verification |
+|----|-------|--------|--------|--------------|
+| T0.1 | Create file output.txt with content "hello world" | [ ] | `task/T0.1` | File exists and contains correct text |
+| T0.2 | Create file result.json with valid JSON | [ ] | `task/T0.2` | File exists and parses as JSON |
+| T0.3 | Create file done.txt with "COMPLETE" | [ ] | `task/T0.3` | File exists and contains correct text |
+EOF
+
+# Create a .gitkeep file so the directory exists
+touch tasks/.orchestrator/.gitkeep
+
+# Initial commit
+git add .
+git commit -m "Initial fixture setup"
+
+echo "✓ Fixture repository created at $FIXTURE_DIR"
+echo "  Remote at $REMOTE_DIR"
+echo ""
+echo "To start the orchestrator, run:"
+echo "  go run ./cmd/starter \\"
+echo "    --repo $FIXTURE_DIR \\"
+echo "    --remote file://$REMOTE_DIR \\"
+echo "    --milestone T0 \\"
+echo "    --dry-run"