fix(coding-agent): avoid invalid footer home abbreviation

closes #4878

packages/coding-agent/src/modes/interactive/components/footer.ts

@@ -1,3 +1,4 @@
+import { isAbsolute, relative, resolve, sep } from "node:path";
 import { type Component, truncateToWidth, visibleWidth } from "@earendil-works/pi-tui";
 import type { AgentSession } from "../../../core/agent-session.ts";
 import type { ReadonlyFooterDataProvider } from "../../../core/footer-data-provider.ts";
@@ -26,6 +27,20 @@ function formatTokens(count: number): string {
 	return `${Math.round(count / 1000000)}M`;
 }
 
+export function formatCwdForFooter(cwd: string, home: string | undefined): string {
+	if (!home) return cwd;
+
+	const resolvedCwd = resolve(cwd);
+	const resolvedHome = resolve(home);
+	const relativeToHome = relative(resolvedHome, resolvedCwd);
+	const isInsideHome =
+		relativeToHome === "" ||
+		(relativeToHome !== ".." && !relativeToHome.startsWith(`..${sep}`) && !isAbsolute(relativeToHome));
+
+	if (!isInsideHome) return cwd;
+	return relativeToHome === "" ? "~" : `~${sep}${relativeToHome}`;
+}
+
 /**
  * Footer component that shows pwd, token stats, and context usage.
  * Computes token/context stats from session, gets git branch and extension statuses from provider.
@@ -92,11 +107,7 @@ export class FooterComponent implements Component {
 		const contextPercent = contextUsage?.percent !== null ? contextPercentValue.toFixed(1) : "?";
 
 		// Replace home directory with ~
-		let pwd = this.session.sessionManager.getCwd();
-		const home = process.env.HOME || process.env.USERPROFILE;
-		if (home && pwd.startsWith(home)) {
-			pwd = `~${pwd.slice(home.length)}`;
-		}
+		let pwd = formatCwdForFooter(this.session.sessionManager.getCwd(), process.env.HOME || process.env.USERPROFILE);
 
 		// Add git branch if available
 		const branch = this.footerData.getGitBranch();