docs(readme): add HVTrust badge

[deepujain]

Summary

• add the requested auto-updating HVTrust badge beside the existing README trust badges
• link the badge to SkillSpector's public HVTracker evidence page

Validation

• git diff --check — clean
• verified the badge endpoint returns HTTP 200 with image/svg+xml
• verified the destination page returns HTTP 200 and identifies SkillSpector
• rendered the live SVG locally and confirmed the badge is legible

Risk

• documentation-only change; no scanner or package behavior changes
• the score is served dynamically by the third-party badge endpoint

Fixes #277

[rng1995]

[SkillSpector Review]\n\nApproved. This is a documentation-only badge addition with a valid target and no code-path impact. Current applicable checks pass.

[deepujain]

Rebased the documentation-only change onto current main at signed head f3a97eb. The badge SVG and target page both return HTTP 200, git diff --check is clean, and GitHub checks are rerunning. Ready for re-review.