feat: show 5-char git hash next to hamburger for cache-bust detection

Vite define bakes __APP_VERSION__ (git rev-parse --short=5 HEAD) at build
time — survives bundling into the arch package deploy. Falls back to 'dev'
when not in a git repo. Also fixes two noNonNullAssertion warnings in
place.ts.

3 files changed, 19 insertions, 4 deletions

diff --git a/src/app/App.svelte b/src/app/App.svelte
index 3024a44..41e68ef 100644
--- a/src/app/App.svelte
+++ b/src/app/App.svelte
@@ -301,6 +301,12 @@
 				onClose={(id) => store.closeTab(id)}
 				onNewDraft={() => store.newDraft()}
 			/>
+			<span
+				class="shrink-0 select-none px-1 font-mono text-[10px] leading-none text-base-content/30"
+				title="Build version (git short hash)"
+			>
+				{__APP_VERSION__}
+			</span>
 			<button
 				class="btn btn-square btn-ghost btn-sm mx-1 shrink-0"
 				aria-label="Toggle sidebar"
diff --git a/src/core/metrics/place.ts b/src/core/metrics/place.ts
index 091fe8f..2402e3e 100644
--- a/src/core/metrics/place.ts
+++ b/src/core/metrics/place.ts
@@ -111,8 +111,11 @@ export function interleaveTurnMetrics(
 		}
 		if (bestEntry >= 0) {
 			usedEntries.add(bestEntry);
-			segmentEntry.set(seg, entries[bestEntry]!);
-			segmentEntryIndex.set(seg, bestEntry);
+			const e = entries[bestEntry];
+			if (e !== undefined) {
+				segmentEntry.set(seg, e);
+				segmentEntryIndex.set(seg, bestEntry);
+			}
 		}
 	}
 
@@ -123,8 +126,11 @@ export function interleaveTurnMetrics(
 		while (nextUnused < K && usedEntries.has(nextUnused)) nextUnused++;
 		if (nextUnused < K) {
 			usedEntries.add(nextUnused);
-			segmentEntry.set(seg, entries[nextUnused]!);
-			segmentEntryIndex.set(seg, nextUnused);
+			const e = entries[nextUnused];
+			if (e !== undefined) {
+				segmentEntry.set(seg, e);
+				segmentEntryIndex.set(seg, nextUnused);
+			}
 			nextUnused++;
 		}
 	}
diff --git a/src/vite-env.d.ts b/src/vite-env.d.ts
index 4078e74..2a2b515 100644
--- a/src/vite-env.d.ts
+++ b/src/vite-env.d.ts
@@ -1,2 +1,5 @@
 /// <reference types="svelte" />
 /// <reference types="vite/client" />
+
+/** 5-char git short hash, baked at build time (vite.config.ts `define`). */
+declare const __APP_VERSION__: string;