feat(02-04): add shared skill symlink helper and wire orchestration-to-worker pipeline

- Add ManagedSkillRef type to adapter-utils for cross-package use
- Add createManagedSkillSymlinks() with Windows junction support (D-13)
- Add managedSkills field to worker RunJob and connector config
- Add listRuntimeSkillEntries dependency to orchestration service
- Wire SkillService lazy init in service-graph for runtime skill resolution
- Include prerequisite skill system files from plans 02-01/02-02

src/main/skill-github.ts

@@ -0,0 +1,162 @@
+// ---------------------------------------------------------------------------
+// GitHub REST API skill fetcher -- imports skills without git clone (D-02)
+// Public repos only (D-03). Uses raw.githubusercontent.com for content
+// downloads (does not count against API rate limits per research).
+// ---------------------------------------------------------------------------
+
+/**
+ * Data returned for each skill found in a GitHub repository.
+ */
+export interface GitHubSkillData {
+  skillMdPath: string;
+  markdown: string;
+  inventory: string[];
+  owner: string;
+  repo: string;
+}
+
+interface Logger {
+  info: (...args: unknown[]) => void;
+  warn: (...args: unknown[]) => void;
+  error: (...args: unknown[]) => void;
+}
+
+// ---------------------------------------------------------------------------
+// Commit SHA resolution
+// ---------------------------------------------------------------------------
+
+/**
+ * Resolve the latest commit SHA for a given ref (branch, tag, or HEAD).
+ * Returns the 40-character hex SHA on success, null on error.
+ */
+export async function resolveGitHubCommitSha(
+  owner: string,
+  repo: string,
+  ref?: string,
+  logger?: Logger,
+): Promise<string | null> {
+  const target = ref || "HEAD";
+  const url = `https://api.github.com/repos/${owner}/${repo}/commits/${encodeURIComponent(target)}`;
+  try {
+    const response = await fetch(url, {
+      headers: { Accept: "application/vnd.github.sha" },
+    });
+    if (!response.ok) {
+      if (response.status === 403) {
+        const resetHeader = response.headers.get("X-RateLimit-Reset");
+        logger?.warn(
+          `GitHub API rate limit hit for ${owner}/${repo}`,
+          resetHeader ? `resets at ${new Date(Number(resetHeader) * 1000).toISOString()}` : "",
+        );
+      } else {
+        logger?.warn(`GitHub commit resolve failed: ${response.status} for ${owner}/${repo}@${target}`);
+      }
+      return null;
+    }
+    const sha = (await response.text()).trim();
+    return /^[0-9a-f]{40}$/i.test(sha) ? sha : null;
+  } catch (err) {
+    logger?.error("GitHub commit resolve network error:", err);
+    return null;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// GitHub tree + SKILL.md fetcher
+// ---------------------------------------------------------------------------
+
+/**
+ * Fetch all SKILL.md files from a GitHub repository via the REST API.
+ *
+ * 1. GET the recursive git tree to find all SKILL.md paths
+ * 2. Optionally filter to a specific skill slug directory
+ * 3. Download each SKILL.md via raw.githubusercontent.com
+ * 4. Collect sibling files as file inventory
+ */
+export async function fetchGitHubSkills(
+  owner: string,
+  repo: string,
+  ref: string,
+  requestedSlug: string | null,
+  logger?: Logger,
+): Promise<{ skills: GitHubSkillData[]; commitSha: string }> {
+  const treeUrl = `https://api.github.com/repos/${owner}/${repo}/git/trees/${encodeURIComponent(ref)}?recursive=1`;
+  try {
+    const treeResponse = await fetch(treeUrl, {
+      headers: { Accept: "application/json" },
+    });
+    if (!treeResponse.ok) {
+      logger?.warn(`GitHub tree fetch failed: ${treeResponse.status} for ${owner}/${repo}@${ref}`);
+      return { skills: [], commitSha: ref };
+    }
+    const treeData = (await treeResponse.json()) as {
+      tree?: Array<{ path: string; type: string }>;
+      sha?: string;
+    };
+    const treeSha = typeof treeData.sha === "string" ? treeData.sha : ref;
+    const allEntries = (treeData.tree ?? []).filter(
+      (entry) => entry.type === "blob" && typeof entry.path === "string",
+    );
+    const allPaths = allEntries.map((entry) => entry.path);
+
+    // Find SKILL.md files (at root or nested)
+    let skillMdPaths = allPaths.filter(
+      (p) => p.endsWith("/SKILL.md") || p === "SKILL.md",
+    );
+
+    // Filter to requested slug directory if provided
+    if (requestedSlug) {
+      skillMdPaths = skillMdPaths.filter((p) => {
+        const dir = p === "SKILL.md" ? "" : p.slice(0, p.lastIndexOf("/"));
+        const dirName = dir.split("/").pop() ?? "";
+        return dirName.toLowerCase() === requestedSlug.toLowerCase();
+      });
+    }
+
+    if (skillMdPaths.length === 0) {
+      logger?.info(`No SKILL.md files found in ${owner}/${repo}@${ref}`);
+      return { skills: [], commitSha: treeSha };
+    }
+
+    const skills: GitHubSkillData[] = [];
+
+    for (const skillMdPath of skillMdPaths) {
+      try {
+        // Download content via raw.githubusercontent.com (no API rate limit)
+        const rawUrl = `https://raw.githubusercontent.com/${owner}/${repo}/${ref}/${skillMdPath}`;
+        const contentResponse = await fetch(rawUrl);
+        if (!contentResponse.ok) {
+          logger?.warn(`Failed to download ${rawUrl}: ${contentResponse.status}`);
+          continue;
+        }
+        const markdown = await contentResponse.text();
+
+        // Collect sibling files in the same directory (or subdirectories)
+        const skillDir =
+          skillMdPath === "SKILL.md"
+            ? ""
+            : skillMdPath.slice(0, skillMdPath.lastIndexOf("/"));
+        const prefix = skillDir ? `${skillDir}/` : "";
+        const inventory = allPaths.filter(
+          (p) => p !== skillMdPath && (prefix ? p.startsWith(prefix) : !p.includes("/")),
+        );
+
+        skills.push({
+          skillMdPath,
+          markdown,
+          inventory,
+          owner,
+          repo,
+        });
+      } catch (err) {
+        logger?.error(`Error downloading skill ${skillMdPath}:`, err);
+        continue;
+      }
+    }
+
+    return { skills, commitSha: treeSha };
+  } catch (err) {
+    logger?.error(`GitHub tree fetch network error for ${owner}/${repo}:`, err);
+    return { skills: [], commitSha: ref };
+  }
+}