docs(cli): correct break-even and region filter notes

cmd/multi_service_engine_versions.go

@@ -513,18 +513,18 @@ func adjustRecommendationForExcludedVersions(rec common.Recommendation, instance
 
 // resizeAfterExclusion sets rec to newCount instances with its money fields
 // scaled to match. A count of zero is the caller's drop signal and carries no
-// money. A resize that common.ResizeCount refuses is also returned as zero
-// rather than as a count with unscaled money.
+// money. The caller derives newCount as max(0, rec.Count-excluded) with
+// excluded > 0, so for newCount >= 1 it is always within [1, rec.Count] and
+// common.ResizeCount cannot refuse it; a refusal means that invariant broke,
+// which must not turn into a count with unscaled money.
 func resizeAfterExclusion(rec common.Recommendation, newCount int) common.Recommendation {
 	if newCount < 1 {
 		rec.Count = 0
 		return rec
 	}
 	resized, err := common.ResizeCount(rec, newCount)
 	if err != nil {
-		log.Printf("❌ Dropping recommendation after extended-support exclusion: %v", err)
-		rec.Count = 0
-		return rec
+		panic(fmt.Sprintf("extended-support resize invariant broken: %v", err))
 	}
 	return resized
 }

docs/cli/filtering.md

@@ -39,7 +39,7 @@ cudly --services rds --exclude-accounts sandbox
 --exclude-regions  Exclude recommendations for these AWS regions (comma-separated)
 ```
 
-When `--regions` is omitted, cudly takes the regions from the Cost Explorer recommendations themselves (not from EC2 `DescribeRegions`), so recommendations in regions that only a linked account has opted into are included. Savings Plans are account-level and are always queried once via `us-east-1`; `--regions` is ignored for them, and `--include-regions` / `--exclude-regions` are what narrow Savings Plan results. `--include-regions` and `--exclude-regions` are applied afterwards as a filter on the fetched recommendations (matching each recommendation's region), so they reduce the results but do not change which regions are queried. If both `--regions` and `--include-regions` are set, the queried regions come from `--regions` and the results are then narrowed by the include/exclude lists.
+When `--regions` is omitted, cudly takes the regions from the Cost Explorer recommendations themselves (not from EC2 `DescribeRegions`), so recommendations in regions that only a linked account has opted into are included. Savings Plans are account-level and are always queried once via `us-east-1`; `--regions` is ignored for them, and `--include-regions` / `--exclude-regions` narrow only EC2 Instance Savings Plans, which are tied to a region; Compute, SageMaker and Database plans are region-agnostic and skip the region filter. `--include-regions` and `--exclude-regions` are applied afterwards as a filter on the fetched recommendations (matching each recommendation's region), so they reduce the results but do not change which regions are queried. If both `--regions` and `--include-regions` are set, the queried regions come from `--regions` and the results are then narrowed by the include/exclude lists.
 
 ```bash
 # Only US and EU recommendations
@@ -171,7 +171,7 @@ gross monthly savings = EstimatedSavings + upfront / term months
 break-even months     = upfront / gross monthly savings
 ```
 
-`EstimatedSavings` is already net of the amortized upfront, so the term amortization is added back before dividing. A provider-supplied break-even wins over the formula. No-upfront recommendations (upfront 0) have a break-even of 0 and always pass. A recommendation with an upfront payment whose break-even cannot be computed (negative or non-finite money, or a term other than 1 or 3 years) is dropped, with the reason in the drop summary, because the limit cannot be enforced on it. If net savings are not positive the break-even is infinite and the recommendation is dropped.
+`EstimatedSavings` is already net of the amortized upfront, so the term amortization is added back before dividing. A provider-supplied break-even wins over the formula. No-upfront recommendations (upfront 0) have a break-even of 0 and always pass. A recommendation with an upfront payment whose break-even cannot be computed (negative or non-finite money, or a term other than 1 or 3 years) is dropped, with the reason in the drop summary, because the limit cannot be enforced on it. If gross monthly savings are not positive (net `EstimatedSavings` at or below `-upfront / term months`) the break-even is infinite and the recommendation is dropped. Net savings of 0 give a break-even equal to the term.
 
 **Refused on `--input-csv` runs.** A recommendations CSV carries no break-even column, so this filter has nothing to read. Combining the two flags fails at startup rather than running with the threshold silently unenforced; drop the flag, or filter the CSV before passing it in. Teaching the CSV format to carry the column is tracked in [#1819](https://github.com/LeanerCloud/CUDly/issues/1819).