fix(run): clarify purge info + hint --input/--input-file on stored-input validation failure

[DaveHanns]

Summary

Two small wording tweaks in apify run so users (and, in particular, agents driving the CLI) don't waste turns re-running with different flags trying to figure out what happened.

Motivation

We repeatedly observed the following confusing flow when driving apify run in a project whose stored INPUT.json is missing a required field:

$ apify run
Info: All default local stores were purged.
Error: The input in your storage is invalid. Please fix the following errors:
  - Field productUrl is required

Two things are misleading here:

1. The purge info message overstates what happened. purgeDefaultKeyValueStore already preserves the resolved input key (see the preserveRegExps branch in src/lib/utils.ts), so INPUT.json is NOT wiped by --purge. The current message reads as if it was, which pushes people to try --no-purge next (which yields the same validation error, because the file was never gone in the first place).

2. The validation error offers no way out. Once the user has established the stored input is invalid, the natural next question is "how do I run it once with the missing field filled in?". The CLI does support this via --input '{...}' and --input-file ./input.json, and validateAndStoreInput writes the override to a temp key so the on-disk INPUT.json is not modified — but nothing in the error message points there.

Change

• Clarify the purge info line to say the input key was preserved and point at --no-purge for full preservation.
• Extend the "The input in your storage is invalid" error header to mention --input and --input-file as a way to override the stored input for this run.

Behavior is otherwise unchanged — messaging only, no logic edits.

Evidence (before)

Info: All default local stores were purged.
Error: The input in your storage is invalid. Please fix the following errors:
  - Field productUrl is required

Evidence (after)

Info: All default local stores were purged (the "INPUT" key-value store entry was preserved; pass --no-purge to keep everything).
Error: The input in your storage is invalid. Please fix the following errors (or override the stored input for this run with `--input '{"...":"..."}'` or `--input-file ./input.json`):
  - Field productUrl is required

Test plan

• apify run on a project with a valid INPUT.json — no message change (both lines only appear on the failing path).
• apify run on a project with an INPUT missing a required field — updated purge line + updated error header appear; INPUT.json on disk is untouched (already true today, this PR just tells the user that).
• apify run --input '{"productUrl":"https://example.com"}' on the same project — override path still used; error header (if it were to appear) is the existing --input variant, not the storage variant.

Surfaced during an evaluation of Apify surfaces for agent-driven Actor development.