Pre-existing PHPStan lint failures blocking releases (transcription/callback.php, render.php)

[chubes4]

Context

While releasing v0.14.2 (PR #58 — socials publish refactor) the homeboy release pipeline failed code-quality checks on PHP files unrelated to the PR. The release was unblocked with `--skip-checks`, but the underlying lint debt should be fixed so future releases run clean.

Failing checks (from `homeboy release extrachill-studio` on commit c3c167e)

`inc/transcription/callback.php:189`

```
Function str_ends_with not found.
[function.notFound]
```
`str_ends_with()` is PHP 8.0+. PHPStan likely needs the PHP version target raised, or the call needs a polyfill / compat guard.

`src/blocks/studio/render.php:90`

```
Parameter #1 $text of function esc_attr expects string, string|false given.
[argument.type]
```
A `string|false` value is being passed straight into `esc_attr()`. Needs a `(string)` cast or a `?: ''` fallback.

Top error counts from the run

Type	Count
argument.type	6
return.unionTypeNotSupported	3
method.notFound	3
function.notFound	2
class.notFound	1
function.alreadyNarrowedType	1

Acceptance

• `homeboy release extrachill-studio` runs to green without `--skip-checks`.
• All PHPStan findings above resolved (either fix the code or update the PHPStan baseline / config to reflect intentional decisions).

Notes

• This is not introduced by PR refactor(socials): nuke standalone 'paste external URL' input from publish pane #58 — those errors existed on `main` before the merge.
• No tests directory exists yet — separate concern, worth filing if not already tracked.