[Website] Ask before reloading edited Blueprint fragments

[adamziel]

Changing or removing a Blueprint fragment now asks whether to reload. Without a reload, the address bar can describe a different Blueprint than the running Playground.

Blueprint fragments are read when Playground boots. Before this PR, editing or removing the fragment changed the URL but did nothing to the running instance. Accepting the browser prompt now reloads the page. A replacement fragment boots its Blueprint; removing the fragment boots without a URL Blueprint. Canceling restores the previous URL.

Screencast:

fragment-confirm.mp4

Testing

Open Playground with a Blueprint fragment and replace it with another encoded Blueprint. Cancel and check that the previous URL returns. Repeat and accept to check that the new Blueprint loads. Then remove the fragment and check that accepting the prompt reloads without a URL Blueprint.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds a hashchange confirmation flow so that changing the Blueprint fragment in the URL prompts the user to reload (to boot the new Blueprint) or reverts the URL (to keep the current running Playground consistent).

Changes:

• Introduces confirmReloadWithNewBlueprint to intercept hash-only URL changes and either reload or restore the previous URL.
• Adds a one-time global hashchange listener guarded by a Symbol.for(...) patch key.
• Adds unit tests covering accept/decline flows and ignoring hash removal.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
packages/playground/website/src/lib/state/url/router-hooks.ts	Adds hashchange interception + confirmation/revert logic for Blueprint fragment changes.
packages/playground/website/src/lib/state/url/router-hooks.spec.ts	Adds tests for the new hashchange confirmation behavior.

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