Fix CI: order steps by artifact dependency, resolve fresh-clone builds

CI failed at Lint with 1519 no-unsafe-* errors on every cross-package
import. Three fresh-checkout issues, invisible locally because lib/
persists between runs:

- Lint ran before Typecheck, but the type-aware ESLint config resolves
  vendor packages via their built declarations (tsconfig.typecheck.json
  -> vendor/*/lib), which Typecheck emits. Reordered.
- The first-ever tsc -b resolved sibling vendor plugins through their
  package.json types (lib/index.d.ts, not yet emitted) — TS2307 until a
  second run. The source-level paths map moves from the root
  tsconfig.json (dev-only, not inherited by package builds) into
  tsconfig.base.json so the whole build graph resolves source-first;
  tsconfig.typecheck.json still overrides wholesale to lib resolution.
- Hygiene ran publint (validates packed lib/index.js bundles) before
  Build emitted them. Reordered.

Also: checkout/setup-node bumped v4 -> v6 (node20 runners are
force-switched to node24 on 2026-06-16), the Build step name catches up
with tsdown, and AGENTS.md documents the one case where a fresh clone
needs `yarn typecheck` before `yarn lint`.

tsconfig.base.json

@@ -18,6 +18,28 @@
     "noFallthroughCasesInSwitch": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "types": ["node"]
+    "types": ["node"],
+    // Source-level resolution for the build graph: without this, a fresh
+    // checkout's first `tsc -b` resolves sibling vendor plugins through their
+    // package.json types (vendor/*/lib/*.d.ts) which don't exist yet — TS2307
+    // until a second run. Derived configs that want lib resolution
+    // (tsconfig.typecheck.json) override this map wholesale.
+    "paths": {
+      "cordis": ["./vendor/cordis/src"],
+      "cosmokit": ["./vendor/cosmokit/src"],
+      "schemastery": ["./vendor/schemastery/src"],
+      "@cordisjs/plugin-loader": ["./vendor/loader/src"],
+      "@cordisjs/plugin-include": ["./vendor/include/src"],
+      "@cordisjs/plugin-group": ["./vendor/group/src"],
+      "@cordisjs/plugin-timer": ["./vendor/timer/src"],
+      "@cordisjs/plugin-hmr": ["./vendor/hmr/src"],
+      "@cordisjs/plugin-logger-console": ["./vendor/logger-console/src"],
+      "@deepseek-ai/dsh-llm": ["./packages/llm/src"],
+      "@deepseek-ai/dsh-session": ["./packages/session/src"],
+      "@deepseek-ai/dsh-system-prompt": ["./packages/system-prompt/src"],
+      "@deepseek-ai/dsh-tools": ["./packages/tools/src"],
+      "@deepseek-ai/dsh-agent": ["./packages/agent/src"],
+      "@deepseek-ai/dsh-agent-loop": ["./packages/agent-loop/src"]
+    }
   }
 }