Explorer URL is inconsistent: testnet-endpoints lists explorer.safrochain.com as testnet, mainnet-endpoints lists none

[atomdbc]

Problem

The docs don't agree on which explorer belongs to which network, and mainnet has no explorer documented at all.

Source	Claim
docs/networks/testnet-endpoints.md (line ~60)	https://explorer.safrochain.com/ is the testnet explorer
docs/networks/mainnet-endpoints.md	no explorer listed — RPC, REST, gRPC, seeds, status, and snapshots are all there, but no explorer row
docs/intro.md	https://explorer.safrochain.com/ listed as the explorer, network unspecified
Internal validator handbook	explorer.safrochain.com = mainnet, explorer.testnet.safrochain.com = testnet

So explorer.safrochain.com is simultaneously documented as the testnet explorer and the mainnet explorer, and explorer.testnet.safrochain.com appears nowhere in the docs.

Impact

Mainnet is live and there's no documented way to look up a validator, transaction, or block in a browser. Validator onboarding leans on the explorer to confirm a validator went live and to check active-set standing — right now operators are pointed at a URL that may be showing them a different chain entirely.

What's needed

Confirm which host serves which network, then:

1. Add an explorer row to mainnet-endpoints.md.
2. Correct testnet-endpoints.md if explorer.safrochain.com is in fact mainnet.
3. Disambiguate the bare link in intro.md.

Context

Came up in #21. That PR deliberately avoids citing an explorer and points to status.safrochain.network and RPC queries instead, since stating the wrong one is worse than stating none.