Add human-approved Never Fail Twice learning

[AmIrRX0]

Outcome

Adds a human-gated repository learning loop: capture a reviewed PR as an inert lesson draft, promote it only after maintainer review, and make approved lessons available to future Fixel runs.

What changed

• adds fixel learn --repo owner/repo --pr N
• captures PR descriptions, reviews, inline/conversation comments, and failed checks
• keeps every generated lesson at status: draft by default
• loads only regular, bounded .fixel/lessons/*.md files with status: approved
• preserves the credential, sandbox, network, git, and human-review boundaries after lesson text
• adds the first approved lesson from PR Fix #10: Add a local Codex CLI provider #11 and a deterministic gate benchmark
• documents the English/Persian workflow and prepares v1.2.0

Security boundary

Review and CI content is untrusted evidence. Fixel never approves, commits, pushes, or merges a lesson. Drafts, malformed files, symlinks, and oversized lesson sets are ignored. Optional GitHub evidence sources can fail independently without turning missing data into trusted guidance.

Verification

• 18 automated tests pass
• Never Fail Twice gate benchmark: 1/1
• npm pack --dry-run succeeds
• git diff --check passes
• JavaScript syntax checks pass
• real capture dogfood: PR Fix #10: Add a local Codex CLI provider #11 -> .fixel/lessons/pr-11.md -> manual review -> approved regression rule