Phase 3: add matchReadPathToSkill — read tool path to skill mapping.

Match read paths against registered SKILL.md filePath for the read tracking source.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/detect.ts

@@ -1,3 +1,6 @@
+import { isAbsolute, normalize, resolve } from "node:path";
+import type { Skill } from "@earendil-works/pi-coding-agent";
+
 /** Raw `/skill:name` at start of user input (SPEC §6.2 #1). */
 const SLASH_SKILL_RE = /^\/skill:([a-z0-9-]+)/;
 
@@ -11,6 +14,13 @@ export interface ParsedSkillBlock {
 	content: string;
 }
 
+/** Minimal skill fields for read-path matching (SPEC §6.2 #3). */
+export type SkillPathMeta = Pick<Skill, "name" | "filePath" | "baseDir">;
+
+function normalizePathForCompare(filePath: string): string {
+	return normalize(filePath);
+}
+
 /** Returns skill name when text is a slash skill command, else null. */
 export function detectSlashSkill(text: string): string | null {
 	const match = SLASH_SKILL_RE.exec(text);
@@ -29,3 +39,24 @@ export function parseSkillBlocksFromText(text: string): ParsedSkillBlock[] {
 	}
 	return blocks;
 }
+
+/** Match read tool path to a registered skill SKILL.md (SPEC §6.2 #3). */
+export function matchReadPathToSkill(
+	path: string,
+	skills: readonly SkillPathMeta[],
+): SkillPathMeta | null {
+	const normalizedPath = normalizePathForCompare(path);
+	for (const skill of skills) {
+		const skillPath = normalizePathForCompare(skill.filePath);
+		if (normalizedPath === skillPath) {
+			return skill;
+		}
+		if (!isAbsolute(path)) {
+			const resolvedFromBase = normalizePathForCompare(resolve(skill.baseDir, path));
+			if (resolvedFromBase === skillPath) {
+				return skill;
+			}
+		}
+	}
+	return null;
+}