apply_patch: `*** End of File` anchor is dead code and never anchors to the end

Bug description

The *** End of File anchor in apply_patch updates is parsed but never takes effect: packages/opencode/src/patch/index.ts parseUpdateFileChunks guards the change-line loop with !lines[i].startsWith("***"), so the *** End of File line can never enter the loop body and is_end_of_file stays undefined forever. The tryMatch EOF branch (match from end of file first) therefore never runs, and EOF-anchored patches silently fall back to plain forward matching, editing the first occurrence of the pattern instead of the last.

The reference parser in packages/core/src/patch.ts implements the same marker correctly (loop only excludes @@; the EOF marker is checked inside the body, and other *** lines break the loop).

Reproduction

File eof_anchor.txt containing marker\nend\nmiddle\nmarker\nend (no trailing newline), patch:

*** Begin Patch
*** Update File: eof_anchor.txt
@@
-marker
-end
+marker-changed
+end
*** End of File
*** End Patch

Expected: last marker occurrence edited (marker\nend\nmiddle\nmarker-changed\nend). Actual: first occurrence edited.

Environment

• OS: Windows
• opencode version: dev branch