Tasks

• src/config.rs: AccountConfig::email and AccountConfig::display_name, aliased to from and from-name; the global Config::display_name, aliased to from-name; both keys added to RENDER_ORDER so a generated account leads with its identity.
• src/account/context.rs: the two fields on the runtime Account, merged account-over-global, plus resolve_from, which resolves the --from override against them and hands back the address and the name apart.
• src/shared/message/builder.rs: BuilderArgs::from_name, and Address::new_address instead of the bare &str, so mail_builder encodes the name.
• src/shared/message/{compose,reply,forward}.rs: the default resolved through account.resolve_from, and the --from help naming it.
• src/wizard/discover.rs: prompted_email reading the prompt back as an address, written onto the generated account; a URL's userinfo is not one.
• Tests: the name-with-a-comma coming out quoted, the global name pairing with the account address, and --from dropping the configured name; the shapes prompted_email refuses.
• himalaya-tui: email and display-name accepted as aliases of from and from-name, its own spec and log entry.
• config.sample.toml and the CHANGELOG entry.
• Fold the delta into cairn/spec/config.md, cairn/spec/commands.md and cairn/spec/wizard.md; write cairn/log/2026-08-16-compose-from-identity.md.