Add deploy-cli.sh: ship the CLI as a single bundled file, no git clone needed

The CLI only touches Node builtins and libsodium-wrappers (no native
addons like better-sqlite3, which the server needs but the CLI never
imports) -- confirmed by checking its actual import graph, not assumed.
That makes it a good candidate for a single-file esbuild bundle rather
than requiring a full git checkout + npm install on every machine that
needs to run `keep pull`.

deploy-cli.sh bundles src/cli (~18kb) and ships it straight to a host
over SSH -- HOST=user@vps ./deploy-cli.sh -- mirroring flit's
deploy-daemon.sh ssh-cat-chmod pattern rather than inventing a new
convention. No git, no npm install, no node_modules on the target at
all, just the one file plus a `node` runtime already there from
whatever else is deployed on that box.

Caught a real bug while building this: --banner:js="#!/usr/bin/env
node" duplicated the shebang esbuild already preserves from the source
file automatically, landing it on line 2 instead of line 1 -- Node
only special-cases a shebang on line 1, so the bundle threw a syntax
error on every invocation until the redundant banner flag was removed.

Verified the bundle for real, not just that it builds: ran `keep
identity init` / `identity show` against it directly and confirmed a
real Ed25519 keypair comes out the other end -- the specific thing
worth checking given libsodium-wrappers needed a createRequire
workaround for its own broken ESM packaging, and bundling could easily
have broken that differently.

Also documents both CLI-provisioning paths in INTEGRATION.md
(scripts/install-cli.sh for a machine you're fine cloning onto,
deploy-cli.sh for one you'd rather not) as a "getting keep onto a
machine" prerequisite section, ahead of the existing deploy-pattern
docs that all assume it's already there.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package-lock.json

@@ -21,6 +21,7 @@
         "@types/express": "^4.17.21",
         "@types/libsodium-wrappers": "^0.7.14",
         "@types/node": "^22.0.0",
+        "esbuild": "^0.28.1",
         "tsx": "^4.15.0",
         "typescript": "^5.5.0"
       }