refactor: replace 7-step scout scaffolding with sequential-thinking approach

feat: add Todo Management rule to all subagent system prompts

fix: per-file exclusion check in step (3) of scout prompts

fix: todowrite as mandatory first action in scout and research prompts

fix: front-load mechanical steps before task context in scout prompts

fix: resolve gate conflict with mid-step write-out checkpoints

fix: require explicit research plan write-out in research-brief

fix: require explicit written decisions at every scout classification step

fix: add explicit exclude-identification step to all scout procedures

fix: add verbatim dispatch contract to git-context, research-brief, write-dag

fix: add verbatim dispatch contract with what/why/bad-good to scout templates

fix: steps-before-questions and file-only step (2) in scout subagent prompts

fix: remove 'relevant to area' qualifier from scout-parallel step (2)

fix: remove agent output format overrides and replace skip-list glob with classify-then-glob

fix: improve ExternalScout tool usage instructions in research-brief dispatch