fix(baseapp): make BaseApp.Close idempotent

[pucedoteth]

Description

Closes #26558

server/start.go defers two cleanups that each call app.Close():

• startCmtNode returns a cleanupFn that stops the CometBFT node and then calls app.Close() — deferred at server/start.go:352
• startApp returns an appCleanupFn that shuts telemetry down and then calls app.Close() — deferred at server/start.go:252

Defers run LIFO, so on the ordinary in-process shutdown path both fire and Close runs twice. Close closed app.db and app.snapshotManager unconditionally, so the second call re-closed an already-closed database.

Backends disagree about what that means. goleveldb returns an error, which is merely logged. pebble panics with pebble: closed, so a pebble-backed node panics at the tail end of an otherwise clean stop and exits non-zero.

Fix

Guard the shutdown with a sync.Once and replay the first call's result. The underlying resources are closed once regardless of how many cleanup paths call Close, and a genuine close error is still surfaced to every caller rather than being swallowed.

This is deliberately fixed in BaseApp.Close rather than by deleting one of the two defers: Close is exported, and the SDK itself calls it from four separate places (server/start.go lines 328, 424, 649, 830). Making the method idempotent fixes all of them, and any chain doing the same in its own start command.

Testing

baseapp/close_test.go wraps a dbm.DB so the second Close panics the way pebble does, and asserts the backend is only closed once:

• TestBaseAppCloseIsIdempotent — three Close calls, one backend close, no panic
• TestBaseAppCloseReplaysError — an error from the first close is still returned by later calls, not lost

Both fail on main (panic: pebble: closed) and pass with this change. Full ./baseapp/ suite, go vet, and gofmt are clean.

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Author Checklist

• included the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• targeted the correct branch
• provided a link to the relevant issue or specification
• reviewed "Files changed" and left comments if necessary
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• updated the relevant documentation or specification, including comments for documenting Go code
• confirmed all CI checks have passed

[greptile-apps]

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