feat(rules): populate Signal bars on 8 remaining cost detectors

[abhinav-1504]

What

Populates the Signal field on 8 cost detectors that previously
returned an empty Signal{}, enabling the inline ratio bars in the
ASCII report.

Why

Fixes #13

How

• oversized_limits.go — CPU/memory request vs limit ratio with
  "limit > 4 vCPU / limit > 16 GiB" note
• excessive_replicas.go — threshold (20) vs actual replica count
• tiny_request.go — actual request vs 10m/32Mi sentinel values
• incomplete_request.go — HaveDisplay: "unset",
  WantDisplay: "required" for the missing-dimension case; numeric
  bar is skipped when Have/Want are both 0, showing only the label text

Testing

• go test ./pkg/rules/... -v — all PASS
• go build ./... — clean
• optiqor demo shows ratio bars for:
  • megabox → CPU limit > 4 vCPU bar, memory limit > 16 GiB bar,
    replica count bar
  • incomplete → CPU sentinel bar, memory unset label
  • memhog → CPU unset label, memory sentinel bar

Checklist

• PR title follows Conventional Commits
• All commits are DCO-signed
• No unrelated changes pulled in
• No LLM calls or telemetry introduced
• No proprietary backend imports

[github-actions]

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[abhinav-1504]

Hello @btwshivam,
Populated the Signal field on 8 cost detectors that previously returned an empty Signal{}, enabling the inline ratio bars in the ASCII report.

Waiting for your review!!