feat: configurable default project/repo for issue-create payloads (#270)

[fdaviddpt]

Context

gl-issue-create required project in every payload and gh-issue-create required repo — boilerplate on the most common path, and a runtime missing required field when forgotten. This adds a default-resolution layer so the common case is zero-config.

Resolution order (most specific wins):

1. explicit field in the payload
2. defaults.gitlab_project / defaults.github_repo in .supertool.json (cwd or any parent)
3. the origin git remote, host-matched (gitlab / github.com) — the "nice-to-have" auto-detect from the issue

Changes

• presets/_remote_default.py (new) — shared resolver: config_default (walks up for .supertool.json), parse_remote (scp / ssh:// / https:// forms), origin_slug (host-matched), resolve (config > remote).
• presets/{gitlab,github}/issue_create.py — fill project/repo from the resolver before validation when the payload omits it. Unchanged when present.
• Tests — tests/test_remote_default.py (new, 23 cases: URL parsing, config lookup, origin matching, precedence). tests/test_issue_create.py — the two missing-field tests now disable auto-detect (behavior genuinely changed: with a github origin present, repo would otherwise resolve), plus two new defaulting tests.
• Docs — .supertool.example.json defaults block + comment; docs/presets/{gitlab,github}.md sections. The repo's own .supertool.json now sets github_repo (dogfood).

Test plan

• Full suite: 3108 passed, 34 skipped, coverage 87.57% (gate 86%)
• Real origin auto-detect against this repo: github.com → Digital-Process-Tools/claude-supertool, gitlab → None

Closes #270

🤖 Generated by Max