[bug] : Sortable generator makes timestamps its own decoder rejects, and one bad clock reading breaks the generator for good #55

What's wrong

There are two linked problems in createSortableId.

1. It makes timestamps its own decoder rejects.
Since #29, getTimestamp refuses decoded values above 2^48−1 ms (the year 10889). The generator only checks that the time fits the character width, and 9 base62 characters can hold far more than 2^48.

const s = createSortableId({ now: () => 2 ** 48 })("evt");
// "evt_1HvWXNAa8rJNAzRwphhk3h53w", with no error
getTimestamp(s);   // undefined

const us = createSortableId({ now: () => 1760000000000000 })("evt"); // a microsecond clock
getDate(us);              // undefined
getTimestampOrThrow(us);  // TypeError: prefid: "evt_…" is not a well-formed sortable id.

The same happens with timestampSize: 12 plus now: () => 2 ** 50, and with BASE32_CROCKFORD at 2^48 ("e_8000000000…"). A monotonic spill-over at exactly 2^48−1 also makes unreadable IDs. The value 2^48−1 itself round-trips.

2. One bad clock reading breaks the generator for good.
In src/generators/sortable.ts, lastTime and lastRandom are saved before encodeTime checks the value. After one out-of-range reading, every later call reuses the bad time.

let first = true;
const g = createSortableId({ now: () => (first ? ((first = false), 62 ** 9) : Date.now()) });
for (let i = 0; i < 4; i++) { try { g("e"); } catch (e) { console.log(e.message); } }
// 4 x: prefid: timestamp 13537086546263552 does not fit in 9 "0".."z" characters.

The clock is back to Date.now(), but every call still throws. If the first reading is 2 ** 48 + 5 instead, nothing throws, but every later ID is pinned above 2^48 and decodes to undefined:

e_1HvWXNAaDDAoZvLOKweCFDoAh undefined
e_1HvWXNAaDDAoZvLOKweCFDoAi undefined

Why it matters

now is documented for custom clocks and epochs. Passing microseconds by mistake is plausible, and then every ID is "not well-formed" with no error when it's created. One clock glitch shouldn't poison a long-running process.

What to do

In the generator, compute the candidate time and random indices first. Check them (time <= SORTABLE_TIME_MAX, and the value fits the width). Only then save lastTime/lastRandom. Throw:

RangeError: prefid: timestamp X exceeds the sortable range (2^48-1 ms).

Important: if you add the throw without moving the state update, fixing problem 1 triggers problem 2, so fix both together. Raising the decoder's ceiling instead would undo #29.

Acceptance criteria

• now: () => 2 ** 48 throws a RangeError with default options, with timestampSize: 12 and with BASE32_CROCKFORD.
• 2^48−1 still works.
• A spill-over past 2^48−1 throws, and the next call with a normal clock works.
• Both poisoning repros above: after one bad reading, the next normal reading gives a correct, decodable ID.
• A CHANGELOG "Fixed" entry.

Files: src/generators/sortable.ts, test/sortable.test.ts, CHANGELOG.md