fix(progress): graph/increment task stays "running" on Ctrl+C abort

[HumanBean17]

Problem

When the operator hits Ctrl+C during the graph phase of indexing, the [graph]/[increment] task is left visually "running" in the progress renderer — no terminal event is emitted.

Root cause

_run_cocoindex_update_impl wraps its _popen_capturing_stderr call in a try/finally that emits a parent-side terminal event (status="failed"/"done") for the vectors task — see `src/java_codebase_rag/pipeline.py` (on_progress(ProgressEvent(kind="vectors", ..., status="failed"))).

run_build_ast_graph and run_incremental_graph call _popen_capturing_stderr bare — no finally, so on abort the graph task never gets a terminal event.

Why it surfaced now

Follow-up to #414, which made Ctrl+C actually interrupt the indexing wait (proc.wait() is now called before the uninterruptible Thread.join()). Abort is now reliable, so this rendering gap is actually reachable.

Fix (sketch)

Mirror the cocoindex path: wrap the _popen_capturing_stderr call in both graph functions with a try/finally that emits a terminal ProgressEvent(kind="graph", ..., status="failed") (and "done" on success), based on the returned code — same shape as the vectors finally.

Acceptance

• Ctrl+C during the graph phase renders a red cross / failed marker for the graph task (not a perpetual spinner).
• A passing graph build still renders the done marker.