fix(review): address trail + CI findings on scope context and allowlist

Four review findings and one lint failure, all confirmed real:

• Commit cap kept the OLDEST commits (first lines of --reverse output) and silently dropped everything near HEAD, while the prompt forbids re-deriving scope. Cap newest-first, then reverse the kept slice for reading order — recent commits are the ones a review can least afford to lose. (Cursor Bugbot, high)
• Inline diff budget 48KiB could exceed Windows' ~32KiB CreateProcess command-line cap (prompt travels as argv and ENTIRE_REVIEW_PROMPT). Lowered to 24KiB. (Copilot)
• A diff containing ``` (any markdown-touching change) closed the diff fence early, letting diff content escape into instruction position. Fence is now one backtick longer than the longest run in the diff. (Copilot)
• Bash(git branch:*) allowed mutating -d/-D/-m; removed from the read-only allowlist. (Copilot)
• guidedProfileTask's profileName parameter became unused when the built-in fallback was removed; parameter dropped. (revive)