fix: remove required variables from ADR template

[ckrough]

Summary

• Fixes ADR template missing variables error during project initialization
• Converts template from Jinja2 variables to plain text placeholders

Changes

• Modified src/agentspaces/templates/skeleton/docs/adr/000-template.md
• Removed adr_number and adr_title from required variables
• Replaced Jinja2 placeholders with static text (ADR-XXX, YYYY-MM-DD, Proposed)

Problem

The ADR template required variables (adr_number, adr_title) that are only known when creating specific ADRs after project initialization, causing agentspaces project create to fail with "Missing required variables" error.

Solution

Convert template to static reference file with clear placeholders. Template now renders successfully during project init and serves as a scaffold for users creating new ADRs.

Testing

• ✅ All 288 tests pass (84% coverage)
• ✅ Project creation works without errors
• ✅ Template renders with correct placeholders
• ✅ Python language pack integration verified
• ✅ Code review approved (@Python-pro, @code-reviewer)

Verification

# Quality checks passed
uv run ruff format src/ tests/    # ✓ 57 files unchanged
uv run ruff check src/ tests/     # ✓ All checks passed
uv run mypy src/                  # ✓ 31 files clean
uv run pytest -v --cov=src        # ✓ 288/288 tests pass, 84% coverage

Fixes: agentspaces-qfu

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.