Phase S: hotspot remediation plan (issue #572)

[randlee]

Summary

• Critical review of GitHub issue repowise(sc-compose): hot-spot action plan [sc/repowise-update2] #572's proposed hotspot fixes against actual code, sourced from the repowise dataset refreshed on sc/repowise-update2 (PR repowise(sc-compose): update codebase intelligence #571).
• Adds docs/plans/phase-S.md (phase stub/index per Phase P precedent), four dependency-aware sprint plan docs under docs/phase-S/, and a docs/project-plan.md index entry.
• Approves 8 bounded refactor targets; rejects 4 byte-identical vendored sc-publish script/test duplicates as out of scope; records a CLAUDE.md boundary verdict for every target.
• Every sprint plan embeds literal gh stack commands (init/add, submit --auto, view --json, merge --yes) for that sprint's own PR stack.

This is a planning-only PR — no production code changes.

Test plan

• cargo fmt --all --check
• Phase S plan contract check (frontmatter, canonical sections, gh-stack commands, project-plan linkage)
• git diff --check
• plan_gate QA via quality-mgr (req-qa, arch-qa)

🤖 Generated with Claude Code (team-lead orchestration)

[randlee]

@/private/tmp/claude-501/-Users-randlee-Documents-github-sc-compose/8398afb7-9b28-472d-bc40-ac36cb0f83fa/scratchpad/qa-pr575-plan-gate-report.md

[randlee]

@/private/tmp/claude-501/-Users-randlee-Documents-github-sc-compose/8398afb7-9b28-472d-bc40-ac36cb0f83fa/scratchpad/qa-pr575-plan-gate-r2-report.md