docs: reconcile diverging history only by merge (improvise-1xfb.1)

agent-rules gains rule 8, which forbids rebase, squash in any form, reset
that drops commits, amending a pushed commit and force-push. Rule 7 keeps
the SHA pinning for merge, merge-base and diff. The user's reason is quoted
in the rule: the merge structure of git history is a causal record.

AGENTS.md: the fix-after-merge recipe is now a merge. The wrong-base
rebuild stays the one sanctioned cherry-pick, with -x, and the text says
why no merge can do it. Merge PRs with a merge commit, never squash or
rebase. Also bounds test loops that walk a state machine until a step.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

.agents/skills/code-review/SKILL.md

@@ -27,7 +27,7 @@ them here would let the copy drift:
 | `context/design-principles.md` | The "why" — functional-first, polymorphism over conditionals, correctness by construction, layering, §7 testing doctrine |
 | `context/repo-map.md` | The "where", plus **numbered gotchas** — read the ones your diff touches |
 | `prolog-sessions/kb.pl` | Executable knowledge: `invariant/2`, `doctrine/2`, `forbidden/2`, `decision/3`, and prior `work_done/3` |
-| `AGENTS.md` | Working rules: bug-first tests, `Option`/`Result`/`Box` at the edges, merges over rebases |
+| `AGENTS.md` | Working rules: bug-first tests, `Option`/`Result`/`Box` at the edges, history reconciled only by merge (no rebase, squash or force-push) |
 | `.agents/skills/wave/agent-rules.md`, "GitHub" | The reviewer's rule: what to read before your first comment, how to answer each existing review, and what every review you post must state. Read it before reviewing a PR |
 
 `kb.pl` is the highest-value and least-obvious of these. Grep it before