docs(enrichers): standardize the per-enricher chapter template (#28)

[Metbcy]

Summary

Restructures the seven per-enricher doc chapters under docs/src/enrichers/ to a single eight-section template, in the same order across every chapter. Closes #28.

The content is reorganized, not rewritten: existing prose moves under the canonical headings.

The template

Every chapter now has these sections in this order:

1. Why this signal
2. Algorithm
3. Threshold
4. Output
5. Network
6. Disabling
7. Calibration
8. See also

Chapters touched

typosquat.md, osv-cve.md, version-jump.md, maintainer-age.md, epss.md, kev.md, registry.md, plus a one-line overview.md fix.

Sections that genuinely do not apply carry an N/A note rather than an invented fact. The pure-compute signals (typosquat, version-jump) state that they never touch the network and have no --no-* flag, pointing instead at the knob that does control them.

Overview fix

overview.md listed version-jump's calibration as a hard-coded MIN_MAJOR_DELTA = 2. That is stale: the value is tunable via --multi-major-delta <N> (v0.9.7, default 2). Verified against src/cli.rs (the multi_major_delta field) and src/enrich/version_jump.rs (enrich_with reads the flag, falling back to MIN_MAJOR_DELTA). Corrected the row to match the source and the six other docs that already document the flag.

Testing

• mdbook build: clean, no broken links
• Section audit: all seven chapters carry the eight canonical headings in identical order

Docs only, no .rs changes.

Closes #28.

[github-actions]

Coverage report

Line coverage: 83.6% (9179 / 10976 lines)

Full lcov report available as workflow artifact coverage-lcov: download from this run.

_{v0.9.8 introduces this report; --fail-under-lines will be added once coverage is visible across 2–3 releases.}