agoric publish uses poor, bespoke key management

[dckc]

Describe the bug

agoric publish requires a plain text mnemonic in ~/ag-solo-mnemonic (where ~ is specified using --home). This is unsuitable for production use. Even for dev / test usage, it's questionable.

To Reproduce

1. use agoric run ... to build a bundle (see below)
2. try to publish it with agoric publish
3. Error:

$ agoric publish /home/connolly/.agoric/cache/b1-10d640ccc3f09d37719d87bf33b4cf2cf950da2a5daf7b2c927e5b4569e65e03950fa36be3591e33250906a98e6c39f79fd4cfb5fe1b38f5aff8a115ccfe3846.json
agoric: (Error#1)
Error#1: Required flag for agoric publish: -h, --home <directory>, containing ag-solo-mnemonic
  at publishMain (file:///home/connolly/projects/agoric-sdk/packages/agoric-cli/src/main-publish.js:21:11)

Expected behavior

key management compatible with agd, including either ledger support or docs on how to use authz with a ledger.

agoric publish should ideally be a nicer devex than agd tx swingset install-bundle ...

Platform Environment

• what OS are you using? what version of Node.js?

$ uname -a
Linux bldbox 5.15.0-91-generic #101-Ubuntu SMP Tue Nov 14 13:30:08 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
$ node -v
v18.17.1

• is there anything special/unusual about your platform?
• what version of the Agoric-SDK are you using? (run git describe --tags --always)
  @agoric/[email protected] aka 9f3232b
  just a few commits from master at e0447b8

Additional context

While starting integration testing on #8113 , I ran the builder, which concludes by reminding me to install bundles:

~/projects/agoric-sdk/packages/builders$ agoric run scripts/vats/replace-provisioning.js 
...
creating gov-provisioning-permit.json
creating gov-provisioning.js
...
Remember to install bundles before submitting the proposal:
  agd tx swingset install-bundle @/home/connolly/.agoric/cache/b1-10d640ccc3f09d37719d87bf33b4cf2cf950da2a5daf7b2c927e5b4569e65e03950fa36be3591e33250906a98e6c39f79fd4cfb5fe1b38f5aff8a115ccfe3846.json
...

I tried using agoric publish instead, which led me to this issue.

Screenshots

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