Context hygiene at insert time: result ids, read stubs, the cap, recall

Harness spec 3.0.0 (context.md, loop.json `context`), in session/results.ts,
applied by the engine when a result goes into the conversation and never
afterwards:

- every result is headed by its id ([#0001]); a read also by the path as
  given, its lines, the file's length and the first 8 hex digits of the
  content's SHA-256; an empty file says so;
- a read of an unchanged file whose lines lie inside an earlier full read is
  a stub naming it; a list/glob/grep repeated with the same arguments and the
  same result is "Same result as #…";
- output over 400 lines or 40,000 characters keeps head and tail with the
  elided line; the full result is kept with the session (a new `results`
  table in sessions.db, gone with the session);
- edit, multiedit, write and apply_patch answer with their hunks under a
  bracket with the new content's hash; a new file is "Created, N lines.";
- recall (new built-in tool) shows any stored result, or a range of it, also
  after a resume; ids are never reused;
- compaction appends the table of the reads still in the conversation to the
  summary.

A stub only ever points at a result still in the conversation, so after a
compaction, an /undo or a rewind the file is read in full. compaction.prune
is gone: cutting old outputs in place threw the prompt cache away (an old
config's key is dropped with a warning). blocks/context.md is in the prompt
wherever recall is offered. Conformance runner for the `context` area (11
cases pass).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/harness.ts

@@ -111,6 +111,27 @@ export const LOOP: {
     running_max: { default: number }
     subagent_steps: { default: number }
   }
+  /** Context hygiene (spec 3.0.0, harness/context.md): the result ids, the texts of a read's
+   *  header, a stub, the elided line, recall; the output cap; what is deduplicated; the table
+   *  compaction adds. */
+  context: {
+    ids: { digits: number }
+    read_header: string
+    read_header_empty: string
+    edit_header: string
+    header: string
+    unchanged: string
+    same_result: string
+    elided: string
+    created: string
+    no_result: string
+    recall_header: string
+    sha_digits: number
+    cap: { max_lines: number; max_chars: number; head_lines: number; head_chars: number; tail_lines: number; tail_chars: number }
+    dedupe: { by_hash: string[]; by_result: string[] }
+    compaction: { heading: string; line: string; rows: number }
+    reasoning: string
+  }
 } = LOOP_JSON
 
 /** The `purpose` argument (harness/purpose.json). */