Add LLM planning report and complete REPORT-001

[rfreel]

Motivation

• Provide a concise planning brief for an LLM to produce actionable work plans that respect the loop contract and verification gates.
• Make the planning item machine-trackable in the PRD so the loop can verify and record completion.

Description

• Add loop/PLAN_REPORT.md containing repo goals, loop contract summary, required plan structure, verification gates, risks, and next-step template.
• Add/verify loop/LOOPSPEC.md documenting the minimal LoopSpec fields, gates, budgets, and stop rules.
• Update prd.json to include the REPORT-001 item and mark it passes: true with notes referencing the new report, and ensure DECIDE-001 is present with LoopSpec references.
• Append a progress entry to progress.txt, add pre-commit success lines to loop/log.txt, and set loop/last_error.txt to the LLM stub message.

Testing

• Ran scripts/ralph/loop.sh which returned success (Loop OK; consider updating prd.json/progress.txt, then commit) and indicated pre-commit checks passed.
• Verified the updated prd.json, progress.txt, and new loop/PLAN_REPORT.md are present and consistent with the acceptance criteria by inspecting the files locally.

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Codex Task