fix(cli): bound --min-savings-pct to 0-100

[cristim]

Closes #2161

Summary

--min-savings-pct was only checked for being finite. That allowed two silent mistakes:

• A negative value behaved as "no filter", because the scorer only filters when MinSavingsPct > 0.
• A value above 100 dropped every recommendation. SavingsPercentage is AWS's EstimatedMonthlySavingsPercentage against on-demand (the comparison is at pkg/scorer/scorer.go:88), so it can never exceed 100.

This PR adds the following:

• validateCoverageAndSavingsPct now rejects values outside [0, 100] with min-savings-pct must be between 0 and 100, got: <v>. Both ends are inclusive, so 0 keeps today's "no filter" default.
• docs/cli/filtering.md documents the range, and CHANGELOG.md has an entry under Fixed.
• The flag-parsing validation table is renamed TestValidateNumericFlagsRejectInvalid, since it now covers out-of-range values as well as non-finite ones.

Validation ordering: the range check runs before the CSV-mode refusal, so --min-savings-pct 150 --input-csv x reports the range error. Both reject the run.

Evidence (local, macOS, GOTOOLCHAIN=go1.26.9; unit tests through the real flag set)

• Fail before / pass after: with the validators.go change stashed, the new min-savings-pct negative and min-savings-pct above 100 cases fail. With the change, they pass, and 100 stays valid.
• Checks:
  • make build passes.
  • go vet ./... passes.
  • go test -race ./cmd/...: 1472 passed.
  • golangci-lint v2.10.1 (the CI pin): 0 issues.
  • scripts/test-git-secrets-allowlist.sh: 44/44.
  • Pre-commit hooks pass.
• Review: an independent non-author reviewer (sonnet, high) did two passes. It confirmed the [0, 100] bound from source, confirmed the CHANGELOG claims, and found no bypass: the flag is the only writer and is validated in PreRunE. Its one low finding, about where the tests sit and what the table is named, is applied.

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📥 Commits

Reviewing files that changed from the base of the PR and between e0a1db6 and 2ca29cc.

📒 Files selected for processing: 4

• CHANGELOG.md
• cmd/validators.go
• cmd/validators_test.go
• docs/cli/filtering.md

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[cristim]

Independent review verdict: CLEAN at 2ca29cc

Reviewer: fresh Claude agent (Sonnet, high effort), not the author. Coordinator: claude-cc-reviewer.

What was checked:

• No sentinels: every MinSavingsPct use is in cmd/: main.go:74 (field), main.go:146 (flag, default 0), multi_service.go:357 (passed to scorer.Config), validators.go:271 (CSV-mode > 0). Tests use 0, 5 and 20, and there are no config-file, env or programmatic setters.
• Wiring: PreRunE: validateFlags (main.go:100) → validateNumericRanges → validateCoverageAndSavingsPct. It runs for every use of the flag and before any network call, and NaN/Inf are rejected first.
• Semantics: checked by the coordinator in the pinned go module. scorer.go:80-81 compares rec.SavingsPercentage < cfg.MinSavingsPct and formats both as %.1f%%, so the value is a 0-100 percentage and the bound matches.
• go vet ./cmd/... is clean, and go test -race -count=1 ./cmd/... passes 1472.

Gate:

• Labels are mirrored from fix(cmd): --min-savings-pct has no range validation #2161.
• Merge waits on CI being green at this SHA. (claude-cc-reviewer)