i18n: the 4-way split of #15178 silently reverted five reviewed fixes

## Problem

https://github.com/Comfy-Org/ComfyUI_frontend/pull/15178 was closed and split into
#15228 → #15229 → #15230 → #15236. Diffing the closed PR's tree against the stack tip
(#15236, which is cumulative since each PR is based on the previous head) shows five
changes that were in the reviewed version and are **not** in the stack.

## The reverts

**1. `parseBatchResponse` silently drops non-string values again** — `scripts/i18n/translate.ts`

```diff
- const invalidIds: string[] = []
for (const [key, value] of Object.entries(parsed)) {
- if (typeof value === 'string') {
- record[key] = value
- } else {
- invalidIds.push(key)
- }
- }
- if (invalidIds.length > 0) {
- throw new Error(
- `translation response has non-string values for ids: ${invalidIds.join(', ')}`
- )
+ if (typeof value === 'string') record[key] = value
```

This is the exact defect reported in
https://github.com/Comfy-Org/ComfyUI_frontend/pull/15062#pullrequestreview-4922889854
and answered with "Fixed in the pending local diff: the parser now rejects every
non-string response value and reports all offending ids." A dropped id is later
reported as `no translation returned`, which is a different and misleading diagnosis.

**2. The plural instruction in `buildSystemPrompt` regressed to the wrong rule**

```diff
- - The | character separates plural forms. Use the target locale's appropriate number of forms and translate each form.
+ - The | character separates plural forms. Keep the same number of forms and translate each form.
```

This is the instruction that was corrected after auditing the corpus and finding that
35 of 46 English `|` strings already have a different form count in at least one
shipped locale. The stack now tells the model to do the thing the audit established is
wrong, and it contradicts #15230's own plural-arity handling.

**3. `maxMalformedResponseRetries` regressed 3 → 1** — `scripts/i18n/translate.ts:21`

**4. `pruneCountFloor` regressed 5 → 25** — `scripts/i18n/config.ts:61`. The floor was
lowered to 5 precisely because 25 is over 10% of `settings.json` (234 leaves) and a
fifth of `commands.json` (124 leaves), which makes the guard meaningless for small files.

**5. The explanatory comment on `chunkItems` was dropped** — the note that the character
threshold is an initial heuristic with recursive splitting as the safety net. Without
it the constant reads as a measured bound.

## Reproduce

```
git fetch origin pull/15178/head:a pull/15236/head:b
for f in scripts/i18n/translate.ts scripts/i18n/config.ts; do
diff <(git show a:$f) <(git show b:$f)
done
```

## Note

The split also introduced genuine improvements that are not in #15178 — `strayLinkPattern`,
`hasEmptyPluralForm` comparing source and target, `printCapped`, and the audit skip-set
derived from `pendingLeaves`. This issue is only about the five items that went backwards.