fix(cli): validate --batch/--limit on backfill-assets instead of silently producing NaN

[pedrofrxncx]

Bug found by reading apps/api/src/cli.ts (the backfill-assets subcommand) — not tied to an issue.

--batch and --limit were passed straight through Number(raw) with no validation (batch: values.batch ? Number(values.batch) : 500, limit: values.limit ? Number(values.limit) : undefined). A malformed value (e.g. --batch abc or --limit -1) silently becomes NaN, which then flows into runPaged's Math.min(batch, remaining) and Kysely's .limit(take) in backfill-assets.ts — producing a confusing SQL-level error deep in the DB layer instead of a clear CLI message at the entry point. This is the same bug class already fixed for SHUTDOWN_DRAIN_MS (#5177), NODE_ENV (#5173), and (in an open PR) DUCKDB_THREADS (#5130) in resolve-config.ts — this one just lives in the CLI flag parser instead of the settings pipeline.

Fix: extracted a small pure parsePositiveIntFlag(flag, raw) helper (apps/api/src/cli/parse-positive-int-flag.ts) that returns undefined when the flag is absent and throws a clear Invalid --batch "abc" — must be a positive integer. error otherwise. cli.ts now calls it for both flags before invoking backfillThreadAssetsCommand, catching and printing the error with process.exit(1) — matching the existing --target validation style right above it in the same command block.

Failure scenario before the fix: deco backfill-assets --batch abc would run past argument parsing and fail later with a raw SQL/driver error instead of telling the user their flag was invalid. Regression test: apps/api/src/cli/parse-positive-int-flag.test.ts covers the missing-flag, valid-value, non-numeric, zero/negative, and non-integer cases.

Reviewer check: bun test apps/api/src/cli/parse-positive-int-flag.test.ts

Locally verified: bun run fmt, cd apps/api && bunx tsc --noEmit, and the targeted test file above all pass. Full CI covers the rest.

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Summary by cubic

Validate --batch and --limit in the backfill-assets CLI to fail fast on invalid input, preventing silent NaN values and confusing SQL errors. Users now get clear, early error messages; defaults remain unchanged.

• Bug Fixes
  • Added parsePositiveIntFlag to parse positive integers or undefined, throwing Invalid --<flag> "<value>" — must be a positive integer. on bad input.
  • Applied it to backfill-assets and exit with code 1 on validation errors, matching existing --target checks.
  • Added unit tests covering missing flag, valid value, non-numeric, zero/negative, and non-integer cases.

^{Written for commit 565a460. Summary will update on new commits.}