Merge step (c): converge to ce-* convention for agents and skills

Aligns local custom agents, skills, and modified shared agents with upstream's
flat ce-<name>.agent.md + ce-<skill>/ convention introduced in upstream v3.x.

Changes:
- Delete 9 upstream-renamed agents for locally-dropped agents (design/*, rails
  reviewers, ankane-readme-writer, data-migration-expert, performance-oracle,
  security-sentinel)
- Delete ce-dhh-rails-style skill (local dropped dhh-rails-style entirely)
- Move 5 custom agents to flat ce-<name>.agent.md paths:
  * python-package-readme-writer, design-conformance-reviewer,
    tiangolo-fastapi-reviewer, zip-agent-validator, lint
- Rename 12 custom skill directories with ce- prefix:
  * john-voice, jira-ticket-writer, hugo-blog-publisher, weekly-shipped,
    proof-push, ship-it, story-lens, sync-confluence, excalidraw-png-export,
    python-package-writer, fastapi-style, upstream-merge
- Port local Python/FastAPI edits into upstream's flat ce-best-practices-
  researcher.agent.md and ce-kieran-python-reviewer.agent.md
- Update frontmatter name: fields in all 17 renamed files to match new paths

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugins/compound-engineering/skills/ce-john-voice/references/revision-checklist.md

@@ -0,0 +1,19 @@
+# Revision Checklist
+
+Run before finishing any piece. Each "yes" requires a rewrite.
+
+## Voice
+- [ ] Does any sentence use an em-dash? → Use parentheses or split the sentence.
+- [ ] Does any abstract noun carry a sentence? ("value," "conviction," "impact," "transformation") → Make it concrete or cut it.
+- [ ] Does any claim dissolve when drilled into? → Add the logic or cut the claim.
+- [ ] Does any hedge weaken without adding nuance? ("somewhat," "in some ways," "it's worth noting") → Cut it.
+
+## Structure
+- [ ] Does the opening start with an abstract thesis or definition? → Rewrite to open on a concrete scene.
+- [ ] Does the conclusion restate or summarize? → Replace with a question, quiet observation, or callback.
+- [ ] Do any paragraphs merely follow each other rather than cause each other? → Reorder or cut.
+
+## Momentum
+- [ ] Does any paragraph feel like it's trudging? → Rewrite until it moves.
+- [ ] Are there runs of similarly-structured sentences? → Break the pattern.
+- [ ] Does the last sentence of each paragraph land or pull forward? → Rewrite if it just stops.