Establish agent engineering foundations for iterative modernization

[fproulx-boostsecurity]

Program context

This PR starts the SmokedMeat modernization program, a continuing sequence of bounded, behavior-preserving architecture deepening iterations. It establishes the repository foundations needed to run that program consistently; it is not itself a production refactor and does not represent the whole program.

Program child: Establish agent engineering foundations for iterative modernization

Initial PR stack

1. This PR - foundation: establish the agent guidance, domain language, durable decision structure, work-tracking conventions, and verification guidance used by later iterations.
2. Next - first architecture decision slice: Modernization 1: define Analysis ingestion architecture, stacked on this PR and tracked by issue 98.

Review and merge this PR before PR 94. Later Wayfinder and implementation work will be tracked separately according to the program's native child issues and dependency relationships.

Outcome

• provide concise agent guidance with progressive disclosure
• establish canonical domain language in CONTEXT.md
• record durable architecture decisions under docs/adr/
• make GitHub Issues and the SmokedMeat Roadmap the work-tracking sources of truth
• provide focused verification guidance for future implementation work

What changed

• replace repository roadmap files with GitHub Issues and the SmokedMeat Roadmap Project
• rebuild the changelog from the published release history through v0.3.1
• add canonical domain language and the Kitchen schema compatibility ADR
• reduce the root agent instructions and route task-specific guidance through focused documents

Why

The repository mixed durable engineering constraints, operational reference material, and stale planning documents in files every coding agent had to load. This change creates a concise entry point, progressive disclosure for specialized work, and one source of truth for public issues and maintainer-owned roadmap ideas.

These foundations support the program guardrails: use canonical domain language, record hard-to-reverse decisions as ADRs, verify in proportion to risk, and keep each modernization iteration independently reviewable.

Impact

Production behavior is unchanged. Coding agents receive less irrelevant context while retaining the repository's non-negotiable rules. Contributors continue using GitHub Issues, while maintainer-owned roadmap ideas remain in the project instead of accumulating as public issues or repository task files.

Validation

• verified release tags and dates against GitHub
• verified referenced documentation paths
• verified documented Make targets
• verified schema 2.5 and quickstart v0.3.1 references against the codebase
• ran git diff --check

Closes #97