fix: scrub Extra Chill bucket-A layer-purity violation from core

[chubes4]

Summary

Scrubs the single bucket-A layer-purity violation enumerated in #2816. Per the platform rule, no plugin in the Data Machine suite may know Extra Chill exists — it is generic, distributable substrate.

The issue triage confirmed core is "overwhelmingly clean": exactly one executable EC literal existed.

Violation fixed

inc/Cli/Commands/ExternalCommand.php:208 — runtime CLI error string for external remove baked extrachill.com/sarai into the operator-facing error message every install prints.

- WP_CLI::error( 'Connection key is required (e.g., "extrachill.com/sarai").' );
+ WP_CLI::error( 'Connection key is required (e.g., "example.com/agent-slug").' );

Replaced with a neutral example.com/agent-slug placeholder matching the format-illustration style used elsewhere. No filter seam needed — this is prose-in-code with no behavior coupling (the data-machine-business#54/#55 apply_filters precedent applies to behavior-affecting defaults, which this is not).

Out of scope (per issue)

• AgentAuthorize.php:438 (*.extrachill.com same-network check) — verified NON-violation; domain resolves at runtime from network_home_url(), EC appears only in a comment. Not touched.
• Bucket B (docblocks, ## EXAMPLES, @param blocks, author/contributor tags) — tracked lower-priority prose noise, left as-is.
• Bucket C (@extrachill/chat npm dep references) — legitimate external dependency, excluded.
• Did not touch inc/Engine/AI/ (reserved by another branch).

Verification

• php -l inc/Cli/Commands/ExternalCommand.php — no syntax errors.
• vendor/bin/phpcs inc/Cli/Commands/ExternalCommand.php — exit 0, clean (no equals-alignment or other findings on the touched file).
• Acceptance grep: no executable EC literals remain; all surviving extrachill.com/sarai matches are docblocks/@param/## EXAMPLES (bucket B).
• Behavior unchanged — single error-string literal swap.

Closes #2816 (bucket-B prose remains as tracked lower-priority cleanup).

[homeboy-ci]

Homeboy Results — data-machine

Lint

✅ lint — passed

ℹ️ Full options: homeboy docs commands/lint
Deep dive: homeboy lint data-machine --changed-since 3cbfc1b

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-lint-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-lint-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/28336277198

Test

✅ test — passed

ℹ️ No impacted tests found for --changed-since 3cbfc1b
ℹ️ Run full suite if needed: homeboy test data-machine
Deep dive: homeboy test data-machine --changed-since 3cbfc1b

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-test-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-test-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/28336277198

Audit

✅ audit — passed

• audit — 2 finding(s)
• Total: 2 finding(s)

Deep dive: homeboy audit data-machine --changed-since 3cbfc1b

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-audit-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-audit-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine/actions/runs/28336277198

Tooling versions

• Homeboy CLI: homeboy 0.269.1+4c0e18d5b697+b2db8f9b
• Extension: wordpress from https://github.com/Extra-Chill/homeboy-extensions
• Extension revision: 392cf7d2
• Action: unknown@unknown