feat(workspace-context): load all instruction candidates, dedup by trimmed content, follow symlinks

Squashes feat/instruction-load-all-dedup and feat/allow-instruction-symlink.

packages/context/workspace-context/src/digest.ts

@@ -14,3 +14,15 @@ import { createHash } from 'node:crypto'
 export function instructionContentSha1(content: string): string {
   return createHash('sha1').update(content).digest('hex')
 }
+
+/**
+ * Compute the whitespace-insensitive identity used for per-directory duplicate
+ * suppression. Leading and trailing whitespace is trimmed before hashing so a
+ * symlinked or byte-copied sibling that differs only by surrounding whitespace
+ * still collapses to a single rendered file.
+ * @param content - exact UTF-8 instruction text.
+ * @returns SHA-1 digest of the trimmed content.
+ */
+export function trimmedInstructionDigest(content: string): string {
+  return instructionContentSha1(content.trim())
+}