Remove spec documents and their citations

[claude-spd1]

Description

Delete the core spec and remove its filename links, numbered citations, and instructions to maintain it. Keep the implementation, explanations, and numerical tests; assertion tests now match descriptive errors rather than retired invariant IDs.

Motivation and Context

Dan requested removal of these documents across the team’s repos because they are not valuable to the workflow (Bridge task 1578).

How Has This Been Tested?

• make check and commit hooks pass (Ruff and BasedPyright).
• Python AST comparison: no executable changes beyond documented error/field-description strings and the two corresponding test matches.
• No remaining spec filename references; YAML changes are comments only.
• Both affected assertion-message tests pass on CPU (2/2; and-gmi job 620901).

Does this PR introduce a breaking change?

No API or numerical changes. The document and its numbered citation convention are removed.

Diff breakdown

• guidance: +75 / -113
• deleted spec: +0 / -507
• comments and documentation strings: +255 / -274
• tests: +146 / -148

Crew-Address: agent/lk9b
Bridge-Task: 1578