fix: validate spot history --limit upper bound (max 15)

[auroraxo]

Closes #22

docs/spot.md documents --limit for jup spot history as defaults to 10, max 15, but the command only rejected non-positive values. --limit 1000 was passed straight through to the API and silently clamped downstream (DatapiClient.getSwapsByAddress does Math.min(limit, 30)), so the user never saw an error even though they asked for far more than documented.

This rejects --limit > 15 before any network call, mirroring the existing lower-bound check:

$ jup spot history --limit 1000
Error: --limit must be between 1 and 15.

Verified locally: tsc --noEmit clean, oxlint src clean, prettier --check src clean. bun test not run here — bun is not installed in this environment; happy to add a unit test if the maintainers would like one.

References:

• docs/spot.md:149 --limit defaults to 10, max 15
• src/clients/DatapiClient.ts:150 Math.min(params.limit, 30) (silent clamp)
• src/commands/SpotCommand.ts:613 (previously only rejected limit <= 0)

[auroraxo]

Added a unit test in 877d2f2 covering the new upper bound and the existing lower bound:

$ bun test src/commands/SpotCommand.test.ts
(pass) rejects limit above the documented maximum of 15
(pass) rejects non-positive and non-numeric limits
2 pass, 0 fail

Full local CI also green: bun run ci (fmt:check, lint, typecheck, test) → 76 pass / 0 fail.