fix(docs): preserve escaped pipes in README cells

[localai-org-maint-bot]

Outcome

Closes a fail-open path in the ROAD-V1-A6 README structure guard. The table-cell budget previously split rows on every |, so escaped Markdown pipes could divide one real oversized prose cell into individually sub-threshold fragments.

The checker now splits only on unescaped delimiter pipes. README content, lifecycle states, support claims, runtime code, models, builds, and benchmark behavior are unchanged.

Design selected

I considered three approaches:

1. reconstruct escaped fragments after raw splitting, which is fragile;
2. add a full Markdown parser dependency, which is disproportionate to this checker;
3. use the repository's existing negative-lookbehind escaped-pipe convention.

This PR uses option 3. The accepted spike and exact anchors are in .agents/specs/readme-escaped-pipe-cell-budget.md.

TDD evidence

RED first on base 1448e981: the new real-behavior mutation failed exactly because readme_errors() returned no errors for one 308-character cell containing escaped pipes.

GREEN on b9620ef2:

• focused README structure suite: 19/19
• complete tests/scripts suite: 96/96
• all eight standalone scripts/check-*.py repository checkers pass
• staged and per-commit document checkpoint checks pass
• git diff-tree --check HEAD passes

No compiler, GPU, model, download, external host, or performance run was used or required. Benchmark disposition is NOT APPLICABLE with benchmark_binding=false.

Slack

The required selection notification and final notification were attempted through the bundled secret-safe sender. No Slack channel is configured; #general returned channel_not_found. No credential was read or exposed.

FOLLOWING_AGENTS_PROTOCOL