v4.64.0

Long documents are read by index, the reranker is a measured switch, and the shared board
refuses to write as an account the clone did not declare.

Added

• kj doc index <file> and kj doc section <file> <heading> (KJC-TSK-1183, issue #2407): a
  markdown document is read by its headings first; one section comes whole, exactly as the file
  has it, up to the next heading of the same or a higher level. Exact title or case-insensitive,
  duplicates named by line; an unknown heading lists the ones available; a heading inside a code
  block is text. --json on both.
• Roles read long documents by index (KJC-TSK-1183): over docs.indexFirstBytes (12000 by
  default), a task file read with --task-file and an ADR in the coder prompt reach the roles as
  their preamble plus headings and the kj doc section command, not whole.
• The reranker is a config switch (KJC-TSK-1181, RAG-D2): rag.search.rerank.{enabled, top_n, model} besides --rerank; kj rag eval --rerank measures with it; without the library the
  install is said once per process. Measured on the frozen corpus: same MRR (0.925), p95 43 → 64
  ms, so it stays off by default (ADR 0026, confirmed by the maintainer).
• kj hu on the shared board refuses a gh account the clone did not declare (KJC-TSK-1186):
  with gh_user in .karajan/identity.local.yml, a different active account stops the command
  before any gh call, naming the exact gh auth switch. Three opaque GraphQL failures in one day.

Fixed

• The bootstrap grace test leaves a second of slack to the marker mtime (KJC-BUG-0396): on
  GitHub runners the mtime sat a fraction of a millisecond ahead of Date.now().