SDD workflow upgrade v0.4.0

[J0hnExample]

Summary

Implements the SDD/context-engineering workflow upgrade for release 0.4.0 from the provided ticket patch.

This adds:

• expert routing profiles for the existing read-only expert workflow
• requirements/design/tasks spec artifact templates
• delta-spec lifecycle with ADDED, MODIFIED, and REMOVED
• read-only spec drift verifier and execution_result.spec_alignment
• conditional steering templates and context-pack selection rules
• quick-flow ticket/prompt with hard escalation thresholds
• decision locks and context budget fields
• README, VERSION, CHANGELOG, and orchestrator ticket closeout for 0.4.0

Safety

• Preserves scoped allowed_files/forbidden_files, no-secrets, no-bulk-staging, approval boundaries, and proof gates.
• Does not introduce a second persona/BMAD team; expert routing remains read-only profile selection.
• Keeps agent/*.md changes generic to the template and avoids local machine notes.

Validation

• Parsed all repository YAML files with PyYAML.
• Ran git diff --check.
• Verified VERSION and README current version are 0.4.0.
• Verified no stale Current version: 0.3.0 in README.
• Ran Markdown relative path link sanity check.
• Ran secret/private-local-path pattern scan.
• Ran read-only final verifier subagent; fixed its initial ticket-status finding and rechecked pass.

Skipped

• markdownlint was not installed, so Markdown style lint was skipped after link sanity checking.
• No product lint/typecheck/build/runtime checks were run because this repository is a workflow/template documentation package and no runtime product code changed.