feat(coder): add hashline editing core + wire audit hooks into dispatch pipeline

Hashline editing: content-hash anchors for edit_file stale-patch detection.
Pure-JS xxHash32, line hash computation, validation with HashlineMismatchError,
256-entry hash dictionary. 6 files in apps/coder/src/services/hashline/.

Audit hooks: emitHook('tool.execute.after') wired in frame-emitter.ts for
completed/failed tool results. emitHook('turn.end') wired at terminal points
in dispatcher.ts (all 5 run functions: native, external, opencode, warm ACP,
claude SDK). Fire-and-forget, non-blocking.

apps/coder/src/services/hashline/constants.ts

@@ -0,0 +1,10 @@
+export const NIBBLE_STR = "ZPMQVRWSNKTXJBYH"
+
+export const HASHLINE_DICT = Array.from({ length: 256 }, (_, i) => {
+  const high = i >>> 4
+  const low = i & 0x0f
+  return `${NIBBLE_STR[high]}${NIBBLE_STR[low]}`
+})
+
+export const HASHLINE_REF_PATTERN = /^([0-9]+)#([ZPMQVRWSNKTXJBYH]{2})$/
+export const HASHLINE_OUTPUT_PATTERN = /^([0-9]+)#([ZPMQVRWSNKTXJBYH]{2})\|(.*)$/