docs: split ADR-0006 into readable paragraphs and drop dash-joined prose

[lesnik512]

A prose pass over the docs to remove AI-writing tells. No rulings, versions, issue numbers, identifiers, code or links changed.

ADR-0006 was a single paragraph of about 130 lines. It is now split into paragraphs, one per topic: the two rules, the /etc/hosts refusal, the oracles and verdict tables, version range, identifier grammar, the document-wide graph walk, and the drive-qualified bind. The long sentences are broken up and every -- is gone. A few contrasts that only added weight now state the point directly. The ones that tell the reader something stay ("measured, not assumed", rule one vs rule two, structural analog vs equivalent).

The smaller edits:

• ADR-0003: three -- asides are now commas, a colon, or their own sentence.
• CONTEXT.md: em dashes inside definitions are colons, commas or parentheses. "the whole point of the table, not an incidental property of it" is now "the reason the table exists".
• AGENTS.md: dashes and emphasis bold are gone. The bold on "never run bare ruff check" stays because it is a real warning.
• README.md: one decorative bold removed.

Deliberately unchanged: the "rather than" contrasts in ADR-0001, ADR-0004 and AGENTS.md that record a decision, the glossary's bold term labels, and ADR-0002 and ADR-0005, which had no tells.

Checked with git diff --word-diff, a script comparing code spans, numbers, links and fences before and after, and lychee --offline with the CI remap.