feat: let mission 17 sign a real event and show what one is

[Jolah1]

Closes #85 in part.

Mission 17 listed the five fields of a Nostr event and then asked which kind number is a text note. Now the learner writes something, the browser signs it with their key, and the app shows the actual event:

kind      1 (short text note)
content   learning what an event really is
pubkey    989c0b76cb563971fdc9bef31ec06c3560f3249...
id        (hash of this event)
sig       (that id, signed)

…with a nudge to run it again with one character changed and watch the id and sig move completely.

Nothing is published. Mission 26 is where broadcasting happens, and the outcome copy is careful not to imply otherwise. The lesson gained a short paragraph on the two computed fields, because "the id is a hash of the contents, and the sig is that id signed by your key" is the idea that makes the rest of Nostr make sense.

The server checks both halves of that claim

Event::verify recomputes the canonical hash, confirms the id really is that hash, and checks the BIP340 signature against the embedded pubkey. Then we compare that pubkey to the npub registered in mission 14, so the event has to be theirs. Verification is offline by construction: the signing check was split out of broadcast_signed_event, so this mission can never reach a relay.

Verified by trying to break it

Against a running backend, one fresh learner per case:

proof	result
garbage, not JSON	rejected
content edited after signing	rejected
validly signed by someone else	rejected
id swapped for a fake hash	rejected
sig swapped for zeros	rejected
the learner's own signed event	accepted

Plus a new browser test (15 assertions) that drives the real flow, asserts all five fields reach the learner, re-derives the id to show it is content-derived, and confirms no relay call is made and the nsec is never sent.

Full suite green: sign-event 15, badge-share 19, passphrase-fork 10, secret-reveal 7/6, publish-confirm 5, mission-prose 3, solo-rank 5. Plus 30 unit, 30 integration, tsc and build clean.

Notes

• needsNsec no longer piggybacks on needsPublishConfirm: mission 17 needs the key but must not warn that something is "public and permanent" when nobody will ever see it.
• The e2e harness now registers a real deterministic npub at mission 14 instead of a placeholder, because mission 17's verifier requires the signing key to match the registered identity.
• No mission added and no path membership changed, so no badge reverts.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
bitpilot	Ready	Preview, Comment	Jul 18, 2026 4:29pm