feat: add devex doc writer pipeline for autonomous feature proposal generation

[notgitika]

Summary

• Adds an archetype-driven pipeline (agents/devex_doc_writer/) that generates CLI DevEx proposals and implementation plans, grounded in actual codebase patterns via pre-indexed knowledge snapshots
• Implements ts-morph based knowledge refresh (agents/knowledge/) that extracts primitives, schema shape, deploy flow, and commands from the CLI and CDK repos
• Two P0 archetypes: new-resource (new service primitive) and scope-widening (expanding existing CLI capabilities like adding Terraform support)
• Pipeline validates inputs, refreshes snapshots, proposes architecture decisions with reasoning, and assembles writer context for LLM invocation
• Includes writer prompt (voice/style/tenets), self-reviewer (14-point checklist), templates for both DevEx docs and implementation plans

What's included

Component	Purpose
agents/devex_doc_writer/SYSTEM.md	Shared engine design (workflow, tenets, metrics, failure modes)
agents/devex_doc_writer/archetypes/	P0 archetype specs (new-resource, scope-widening)
agents/devex_doc_writer/prompts/	Writer persona + self-reviewer quality gate
agents/devex_doc_writer/templates/	DevEx doc + impl plan templates (both archetypes)
agents/devex_doc_writer/main.py	Entry point — validates, refreshes knowledge, assembles context
agents/knowledge/refresh.ts	ts-morph snapshot generator (10 primitives, 9 schema arrays, 21 commands)
agents/knowledge/extractors/	AST-based extractors for primitives, schema, commands, deploy flow

Test plan

• python3 main.py --input examples/config-bundle-input.yaml --dry-run validates inputs and checks snapshot
• python3 main.py --input examples/config-bundle-input.yaml generates 38K char writer context
• cd agents/knowledge && npm run refresh generates both CLI and CDK snapshots
• End-to-end: feed writer-context.md into LLM session, verify it produces a grounded DevEx doc
• Verify generated doc passes self-review checklist