feat(prompt): implement prompt injection slice 4

pi-extension.ts

@@ -9,8 +9,11 @@ import {
 	reinitPath,
 	retrieveContext,
 	buildPreInitHint,
+	buildAdvisoryReminder,
+	buildStrictBypassGuard,
 	modeAllowsPreInitHint,
 	modeAllowsInjection,
+	evaluateStrictBypass,
 	discoverContextWindow,
 	buildInjectionPayload,
 	shouldReinjectForEvent,
@@ -372,7 +375,19 @@ export default function (pi: ExtensionAPI) {
 			};
 		}
 
-		// Maps exist but advisory mode does not permit automatic artifact injection yet.
+		// Slice 4: advisory mode shows a visible lightweight reminder after init.
+		// No root-pair preload, no per-turn reinjection.
+		if (config.promptInjectionMode === "advisory") {
+			return {
+				message: {
+					customType: "pi-project-map-hint",
+					content: buildAdvisoryReminder(),
+					display: true,
+				},
+			};
+		}
+
+		// Maps exist but mode does not permit automatic artifact injection.
 		if (!modeAllowsInjection(config.promptInjectionMode)) {
 			return {};
 		}
@@ -424,7 +439,8 @@ export default function (pi: ExtensionAPI) {
 			return {};
 		}
 
-		// Slice 3b: detect root-pair artifact changes
+		// Slice 3b: detect root-pair artifact changes early. Invalidation always
+		// forces reinjection, even in strict mode, because the context is stale.
 		const currentMtimes = getRootPairMtimes(ctx.cwd);
 		const hasPrevious =
 			lastRootPairMtimes.mapMtime !== undefined ||
@@ -433,12 +449,47 @@ export default function (pi: ExtensionAPI) {
 			hasPrevious && rootPairChanged(currentMtimes, lastRootPairMtimes);
 		lastRootPairMtimes = currentMtimes;
 
-		const eventType = artifactChanged ? "artifact_change" : event?.type;
+		if (artifactChanged) {
+			const decision = shouldReinjectForEvent(
+				{
+					messages: event?.messages,
+					type: "artifact_change",
+					payload: event?.payload,
+				},
+				config.promptInjectionMode,
+			);
+			if (!decision.needed) {
+				return {};
+			}
+			const contextWindow = discoverContextWindow(ctx);
+			const payload = buildInjectionPayload(ctx.cwd, config, contextWindow);
+			return {
+				message: {
+					customType: "pi-project-map-hint",
+					content: payload.content,
+					display: payload.display,
+				},
+			};
+		}
+
+		// Slice 4: strict-mode bypass guard for sensitive actions with missing protocol path.
+		if (config.promptInjectionMode === "strict") {
+			const bypass = evaluateStrictBypass(event, config.promptInjectionMode);
+			if (bypass.guard) {
+				return {
+					message: {
+						customType: "pi-project-map-hint",
+						content: buildStrictBypassGuard(bypass.reason),
+						display: true,
+					},
+				};
+			}
+		}
 
 		const decision = shouldReinjectForEvent(
 			{
 				messages: event?.messages,
-				type: eventType,
+				type: event?.type,
 				payload: event?.payload,
 			},
 			config.promptInjectionMode,