ttyd process leaked on early exit from Evaluate

[tomenden]

Description

When Evaluate() returns early — between Start() and the Record()/teardown() path — the ttyd process is left running indefinitely.

The deferred cleanup at evaluator.go:45 only calls v.close(), which is set to vhs.browser.Close. The terminate() method that kills both browser and ttyd is only reachable via teardown(), which requires Record() to have started.

Affected code paths

Any early return after Start() succeeds but before Record() begins:

• Page.Wait fails (evaluator.go:50-53)
• A SET command fails (evaluator.go:59-63)
• Video dimensions too small (evaluator.go:78-91)
• A Hide block command fails (evaluator.go:106-109)

Additionally, Start() itself doesn't clean up ttyd if browser launch or page creation fails after ttyd is already started.

Reproduction

# Create a tape that triggers an early SET error
echo 'Set Width 0' > /tmp/bad.tape
echo 'Type "hello"' >> /tmp/bad.tape

# Run vhs (it will error due to bad dimensions)
vhs /tmp/bad.tape

# Check for orphaned ttyd
ps aux | grep ttyd
# ttyd process is still running

Expected behavior

All ttyd processes spawned by VHS should be killed when VHS exits, regardless of which code path is taken.