refactor(packages): extract hashline-core package

Move the hash-anchored edit core (hash computation, validation, edit operations, text normalization, chunk formatter, diff utilities, and a runtime-aware xxHash32 binding) into a new @oh-my-opencode/hashline-core workspace package.

The src/tools/hashline-edit/ surface becomes a set of thin re-export shims, so existing import paths in the plugin keep working while the pure logic lives behind a stable package boundary that has no opencode runtime dependencies.

Tests: bun test packages/hashline-core src/tools/hashline-edit

packages/hashline-core/src/index.ts

@@ -0,0 +1,59 @@
+/**
+ * Hashline core public API.
+ *
+ * Hash dependency choice: Option 2.
+ * This package embeds a runtime-aware xxHash32 implementation (`xxhash32.ts`)
+ * that prefers the host runtime's native xxHash32 binding when available and
+ * falls back to a pure-JS implementation otherwise. No package-level dependency
+ * on any specific runtime; the binding is detected via globalThis at call time.
+ */
+export { NIBBLE_STR, HASHLINE_DICT, HASHLINE_REF_PATTERN, HASHLINE_OUTPUT_PATTERN } from "./constants"
+export type { ReplaceEdit, AppendEdit, PrependEdit, HashlineEdit } from "./types"
+export {
+  computeLineHash,
+  computeLegacyLineHash,
+  formatHashLine,
+  formatHashLines,
+  streamHashLinesFromUtf8,
+  streamHashLinesFromLines,
+} from "./hash-computation"
+export { parseLineRef, validateLineRef, validateLineRefs, HashlineMismatchError, normalizeLineRef } from "./validation"
+export type { LineRef } from "./validation"
+export { applyHashlineEdits, applyHashlineEditsWithReport } from "./edit-operations"
+export type { HashlineApplyReport } from "./edit-operations"
+export {
+  applySetLine,
+  applyReplaceLines,
+  applyInsertAfter,
+  applyInsertBefore,
+  applyAppend,
+  applyPrepend,
+} from "./edit-operation-primitives"
+export { getEditLineNumber, collectLineRefs, detectOverlappingRanges } from "./edit-ordering"
+export { dedupeEdits } from "./edit-deduplication"
+export {
+  stripLinePrefixes,
+  toNewLines,
+  restoreLeadingIndent,
+  stripInsertAnchorEcho,
+  stripInsertBeforeEcho,
+  stripInsertBoundaryEcho,
+  stripRangeBoundaryEcho,
+} from "./edit-text-normalization"
+export { canonicalizeFileText, restoreFileText } from "./file-text-canonicalization"
+export type { FileTextEnvelope } from "./file-text-canonicalization"
+export {
+  stripTrailingContinuationTokens,
+  stripMergeOperatorChars,
+  restoreOldWrappedLines,
+  maybeExpandSingleLineMerge,
+  restoreIndentForPairedReplacement,
+  autocorrectReplacementLines,
+} from "./autocorrect-replacement-lines"
+export { normalizeHashlineEdits } from "./normalize-edits"
+export type { RawHashlineEdit } from "./normalize-edits"
+export { createHashlineChunkFormatter } from "./hashline-chunk-formatter"
+export type { HashlineChunkFormatter } from "./hashline-chunk-formatter"
+export type { HashlineStreamOptions } from "./hash-computation"
+export { toHashlineContent, generateUnifiedDiff, countLineDiffs } from "./diff-utils"
+export { generateHashlineDiff } from "./hashline-edit-diff"