Adopt spec-kit + Claude workflow: constitution v1.0.0 + AGENTS.md

[yarikoptic]

Summary

Bootstrap the spec-kit + Claude workflow for this repository. This PR
is a governance + tooling change, not a behaviour change — no Python code
in tributors/ is touched.

• .specify/ scaffolding (commit ed9d07a, [DATALAD RUNCMD]):
  introduces .specify/{templates,scripts,workflows,integrations, extensions,memory}/, the .specify/extensions.yml hook config, and
  the per-command skills under .claude/skills/speckit-*/ that back the
  /speckit.* slash-commands.
• Constitution v1.0.0 (.specify/memory/constitution.md, commit
  cae8c99): five principles ratified, centred on what Tributors is
  for — adequate contributor acknowledgement and automation of the
  bookkeeping that has historically been manual.
• AGENTS.md at the repo root (new, commit cae8c99): canonical
  entry point for AI agents (Claude Code, Codex, Cursor, Aider, …) and
  for humans wanting a quick orientation. Preserves the prior CLAUDE.md
  build/test/style content and points to the constitution as required
  reading.

Why this is the starting point

Going forward, non-trivial work on this repo flows through spec-kit's
phased commands:

/speckit.specify  →  /speckit.clarify  →  /speckit.plan  →  /speckit.tasks  →  /speckit.implement

Each phase produces a reviewable artifact under specs/<###-feature>/
(spec → plan → research/data-model/contracts/quickstart → tasks). The
constitution is the gate every plan is checked against, so it is
ratified first. AGENTS.md is the shared entry point that AI agents
load before proposing changes, so it is created at the same time.

What is intentionally not in this PR

• No changes to parsers, the CLI, the container, or the GitHub Action.
• No new dev dependencies. The constitution's "Style" Quality Gate
  notes that black/pyflakes are operator-installed today and not
  wired into CI; promoting them to a CI-enforced MUST is the one
  recorded deferred TODO and will land in a follow-up PR.
• No spec/plan for a feature — those come in subsequent PRs invoking
  /speckit.specify etc.

Constitution principles (ratified at v1.0.0)

1. Comprehensive Contributor Acknowledgement — inclusive by default;
   bots excluded because not people.
2. Named Contributor Fields Are Sacred (NON-NEGOTIABLE) — once
   truthy, name / email / affiliation / orcid / blog / bio
   in any managed contributor file MUST NOT be overwritten by an
   automated run. (Scoped to named fields to match what the codebase
   actually enforces; container-structure ordering is a SHOULD.)
3. Pluggable Parsers & Shared Cache — every format is a
   ParserBase subclass; cross-parser state flows through .tributors
   indexed by GitHub login.
4. Automation Across Equivalent Surfaces — library, CLI, container,
   and GitHub Action stay in lockstep with matching options.
5. Identity Resolution with Human-in-the-Loop — ambiguous matches
   prompt (or skip); never silently guess.

Plus normative sections on Metadata & Standards Compliance and
Development Workflow & Quality Gates, and a Governance section
designating AGENTS.md as the constitution's delegate for day-to-day
conventions.

Files touched

• .specify/memory/constitution.md (template placeholders → ratified
  v1.0.0)
• AGENTS.md (new; canonical AI-agent guidance)
• (plus the prior .specify/ scaffolding in ed9d07a)

CLAUDE.md is locally excluded (.git/info/exclude) and symlinked to
AGENTS.md on the contributor's checkout; it is not tracked.

Test plan

• Render .specify/memory/constitution.md on GitHub; verify Sync
  Impact Report (HTML comment) is hidden in the rendered view and
  principle headings are at the right level.
• Render AGENTS.md on GitHub; verify the spec-kit command table
  is column-aligned in source and renders cleanly.
• Invoke /speckit.specify "<some toy feature>" in a follow-up
  branch to confirm the spec-kit + constitution loop works
  end-to-end against this baseline.