Accept alternate squash solution

- validate the upstream requirement of exactly two commits
- accept soft reset followed by a replacement commit
- reject resetting to one commit without creating the squashed commit
- document squash validation parity

LevelsCompare.md

@@ -115,7 +115,7 @@ This file records the upstream Ruby setup and validation intent beside the Andro
 | `cherry-pick` | Top commits are "Filled in README..." then "Added fancy branded output". | Same commit message order plus `README.md` tracked. | Equivalent. |
 | `grep` | Answer is TODO count `4`. | Answer is `4`. | Equivalent. |
 | `rename_commit` | Parent commit message is corrected to `First commit`. | No `coommit` remains and `First commit` exists; the in-app rebase editor uses the subject text on a `reword` line as the replacement message. | Equivalent outcome with a single mobile editor step. |
-| `squash` | Commit count is two. | Commit count at most two and "Adding README" remains. | Slightly stricter on preserving the base README commit. |
+| `squash` | Commit count is two. | Commit count is exactly two; interactive rebase and soft-reset/recommit solutions are accepted. | Equivalent. |
 | `merge_squash` | Commit count is three and all long-feature changes are included. | Squash action recorded and a commit exists. | Known gap: Android does not yet verify all squash file/content effects. |
 | `reorder` | `git log` subject order matches `Third.*Second.*First.*Initial`. | Modeled commit order becomes First, Second, Third. | Equivalent relative to Android's oldest-first commit list. |
 | `bisect` | Answer is hash prefix `18ed2ac` after using Ruby/make fixture. | Learner can run `git bisect start`, mark `HEAD` bad and `known-good` good, run `git bisect run ./test-balance.sh`, then answer the last good commit hash. | Same bisect lesson, different fixture and final answer target to keep the Android flow clear without Ruby/make. |