feat: add agent lineage visualization with SVG tree rendering

Add a dedicated /lineage route with custom SVG-based tree visualization
of the agent spawn chain. Nodes are colored by agent type (orchestrator,
researcher, coder, sysadmin, assistant) and display agent ID, type, and
spawn depth. Clicking a node opens a detail panel. Uses sample data
since the API does not yet expose lineage information.

Closes #15

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

implementation-plans/_index.md

@@ -16,3 +16,4 @@
 | #12   | Session history sidebar                                | COMPLETED    | [issue-012.md](issue-012.md) |
 | #13   | Session config sidebar component                       | COMPLETED    | [issue-013.md](issue-013.md) |
 | #14   | Preset configurations                                  | COMPLETED    | [issue-014.md](issue-014.md) |
+| #15   | Agent lineage visualization                            | COMPLETED    | [issue-015.md](issue-015.md) |

implementation-plans/issue-015.md

@@ -0,0 +1,39 @@
+---
+---
+
+# Issue #15: Agent lineage visualization
+
+**Status:** COMPLETED
+**Issue:** https://git.shahondin1624.de/llm-multiverse/llm-multiverse-ui/issues/15
+**Branch:** `feature/issue-15-agent-lineage`
+
+## Acceptance Criteria
+
+- [x] Dedicated `/lineage` route
+- [x] Tree/graph visualization of agent spawn chain
+- [x] Each node displays: agent_id, agent_type, spawn_depth
+- [x] Visual hierarchy reflecting parent-child agent relationships
+- [x] Custom SVG-based rendering (no external graph library needed)
+- [x] Updates as new agents appear in the stream (reactive via `$derived`)
+- [x] Clickable nodes to show agent details
+
+## Implementation
+
+### New Files
+- `src/lib/types/lineage.ts` — lineage types (`LineageNode`, `SimpleAgentIdentifier`), tree builder, color/label helpers, sample data
+- `src/lib/components/LineageTree.svelte` — custom SVG tree visualization with horizontal layout, bezier edges, colored nodes by agent type, click selection
+- `src/routes/lineage/+page.svelte` — dedicated lineage route with tree, legend, and detail panel
+- `src/routes/lineage/+page.ts` — SSR disabled for this route
+
+### Modified Files
+- `src/routes/+page.svelte` — added navigation links to Chat and Agent Lineage
+- `src/routes/chat/+page.svelte` — added Lineage link in header alongside Config button
+
+### Key Decisions
+- Uses sample/demo data since the API does not yet expose lineage information (AuditService is write-only, ProcessRequestResponse does not include lineage)
+- `SimpleAgentIdentifier` type decouples the UI from protobuf Message dependency, making it easy to adapt when real data arrives
+- Horizontal tree layout: root on left, children branching right, computed via recursive leaf-counting algorithm
+- SVG bezier curves for edges, rounded rectangles for nodes
+- Agent type colors: Orchestrator=blue, Researcher=green, Coder=purple, SysAdmin=orange, Assistant=teal, Unspecified=gray
+- Detail panel slides in from right when a node is clicked, showing full agent info and child list
+- Tree layout is fully reactive via `$derived` runes — updating the `agents` array recomputes the tree automatically