feat(graph): add pre-rebuild-check Claude Code skill

[stmcgovern]

Summary

• Add .claude/commands/pre-rebuild-check.md — a Claude Code skill that runs fromager graph check, interprets the output, and recommends constraint fixes
• Update .gitignore to allow .claude/commands/ while keeping other Claude state ignored

The skill guides the assistant to:

• Run graph check against a build's graph.json
• Present conflicts grouped by binding parent (highest leverage first)
• Recommend specific actions (relax specifier, add constraint, upgrade parent)
• Offer ready-to-paste constraints.txt output
• Flag required conflicts as rebuild blockers

Depends on #999 (graph check command).

Closes: #1012

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: b408849d-cde0-49eb-9c90-1892a8768c4d

📥 Commits

Reviewing files that changed from the base of the PR and between 793408e and 7fedf3c.

📒 Files selected for processing (1)

• .claude/commands/pre-rebuild-check.md

✅ Files skipped from review due to trivial changes (1)

• .claude/commands/pre-rebuild-check.md

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📝 Walkthrough

Walkthrough

Adds a new Claude Code skill document at .claude/commands/pre-rebuild-check.md that specifies an interactive workflow for analyzing a fromager build graph (graph.json), parsing CLI flags (--json, --constraints), and deterministically reporting three outcomes: all checks pass (one-line success, optional diff), structural failures (dangling edges/cycles; self-loops treated as warnings), and version conflicts (grouped by binding parent, classify each as “collapsible” vs “required”, provide recommendations and a constraints-generation flow). Also updates .gitignore to ignore .claude/* but keep .claude/commands/.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding a Claude Code skill for pre-rebuild graph analysis.
Description check	✅ Passed	The description is related to the changeset, explaining the new skill, its functionality, and the .gitignore update.
Linked Issues check	✅ Passed	The PR satisfies issue #1012 requirements: creates the pre-rebuild-check.md skill, encodes the graph check workflow, distinguishes conflict types, identifies binding parents, and suggests constraint edits.
Out of Scope Changes check	✅ Passed	All changes are in-scope: the new .claude/commands/pre-rebuild-check.md directly addresses the skill requirement, and .gitignore changes are necessary to include this file.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In @.claude/commands/pre-rebuild-check.md:
- Line 41: The document contains an internal inconsistency between the
"Required" severity wording: one spot states "will fail" (and a header reads
"Required → blocker. write_constraints_file will fail") while another says "will
likely fail"; make the policy wording consistent by choosing one phrasing and
updating both occurrences: either change the stronger instance to "will likely
fail" or the weaker one to "will fail", and ensure the header/severity label
("Required → blocker") and the mention of write_constraints_file reflect the
chosen wording so all references are identical.
- Line 47: The "Constraints block" instruction is wrong — replace the
non-existent `graph check --constraints` flow with the implemented command
`fromager graph to_constraints <graph.json>` so users run `fromager graph
to_constraints <graph.json>` and paste that output into constraints.txt; update
the text under the "Constraints block" heading to reference `fromager graph
to_constraints`, `constraints.txt`, and describe that the command produces a
ready-to-paste constraints block.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: c9d5908c-eba8-4149-b85d-cdf489822c11

📥 Commits

Reviewing files that changed from the base of the PR and between cd32d2e and 71771ab.

📒 Files selected for processing (2)

• .claude/commands/pre-rebuild-check.md
• .gitignore