Ask for last good commit in bisect level

LevelsCompare.md

@@ -119,7 +119,7 @@ This file records the upstream Ruby setup and validation intent beside the Andro
 | `squash` | Commit count is two. | Commit count at most two and "Adding README" remains. | Slightly stricter on preserving the base README commit. |
 | `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 HEAD known-good` and `git bisect run ./test-balance.sh`; Android accepts the discovered bad hash or the final bisect state. | Same lesson, different fixture to keep it playable without Ruby/make. |
+| `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. |
 | `stage_lines` | Staged diff contains first feature line; unstaged diff contains second feature line. | `feature.rb` is staged. | Known gap: Android does not yet model partial hunk staging. |
 | `find_old_branch` | Current branch is `solve_world_hunger`. | Same. | Equivalent. |
 | `revert` | More than three commits and a revert of "Bad commit" exists. | A commit message starts with `Revert`. | Slightly looser; sufficient for current fixture. |