chore(inbox): rename signal source group to "External sources"

[joshsny]

Problem

The inbox signal-sources section grouped external integrations under a header that didn't match its counterpart in the main PostHog app ("Connected tools" there, "External connections" here). The naming should be consistent across both surfaces.

Changes

Renames the signal-sources group header (and its loading skeleton) from External connections to External sources, matching the sibling "PostHog data" group and the corresponding rename in the main app.

How did you test this?

Label-only copy change; verified via grep that both the live header and the skeleton header were updated. No behavior change.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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Created with PostHog from a Slack thread

[trunk-io]

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 87c3d1d.}

[greptile-apps]

_{Reviews (1): Last reviewed commit: "chore(inbox): rename "External connectio..." | Re-trigger Greptile}

[joshsny]

Merge activity

• Jul 30, 10:18 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jul 30, 10:39 AM UTC: Graphite couldn't merge this PR because it failed for an unknown reason (GitHub is reporting that this PR is not mergeable, despite passing required status checks defined by your branch protection rules. Please check your rulesets for additional blocking criteria. Graphite Merge Queue does not currently support rulesets. Please contact Graphite support for further assistance.).

[joshsny]

Can't land this here: PostHog/code is frozen behind the repo-wide BLOCK ALL PRS ruleset (blocks create/update/delete on ~ALL refs), which is also why Trunk can't prepare a test branch and why Graphite reported "not mergeable despite passing checks". Ported to the monorepo as PostHog/posthog#76579 - closing this one in favour of that.