Remove score clamping and retire score bucket labels

[exisz]

Requirement

Score must be the real computed value with no clamping. Negative scores are meaningful and should be preserved/displayed.

Scope

• Remove score clamping from formula computation.
• Stop applying score bucket labels (score:*) because buckets no longer carry useful meaning.
• Ensure UI/API/data all expose the unclamped score.
• Keep visual styling sane without changing the numeric score.

DoD

• Tests/build pass.
• Latest Hermes Agent v0.16.0 displays/API exposes a negative score instead of 0.
• Sync no longer emits/depends on score:* bucket labels.

[exisz]

Implemented on dev in 1cb7aaa.\n\nVerification:\n- dev API: https://dev.isitstable.com/api/v1/hermes-agent/0.16.0 returns score -123\n- dev API: https://dev.isitstable.com/api/v1/openclaw/2026.6.5 returns score -63\n- npm run build: pass\n- npm run lint: pass (existing next/no-img-element warning only)\n- Removed all score:* bucket labels from existing IsItStable issues and deleted empty score:* label definitions.\n\nRefs #140