feat(cli)!: unified load command; deprecate ingest as an alias

omnigraph load is now the single data-write command:
- works against remote graphs (POSTs the server's /ingest endpoint with the
  same bearer/actor resolution as other remote commands) — previously load
  was the only data command forced to open Lance storage directly
- --from <base> opts into fork-if-missing for --branch (the former ingest
  semantics); without --from a missing branch is an error, never a fork
- --mode is now required: overwrite is destructive, so there is no implicit
  default (the old silent default was overwrite)
- output gains base_branch/branch_created (and table sums on remote loads)

omnigraph ingest stays as a deprecated alias (defaults preserved: --from
main --mode merge) that prints a one-line warning to stderr, matching the
read/change deprecation convention; removal in a later release.

Docs updated in the same change: cli.md, cli-reference.md, policy.md,
audit.md, execution.md (unified load section), AGENTS.md quick-flow,
README.md.

BREAKING CHANGE: scripts running omnigraph load without --mode must now
pass it explicitly (previously defaulted to the destructive overwrite).

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

docs/user/cli-reference.md

@@ -9,8 +9,8 @@ Top-level command families and subcommands. Graph-targeting commands accept eith
 | Command | Purpose |
 |---|---|
 | `init` | `--schema <pg>` → initialize a graph (also scaffolds `omnigraph.yaml` if missing) |
-| `load` | bulk load a branch (`--mode overwrite\|append\|merge`) |
-| `ingest` | branch-creating transactional load (`--from <base>`) |
+| `load` | bulk load a branch, local or remote (`--mode overwrite\|append\|merge` is **required** — overwrite is destructive, so there is no default). Without `--from` the target branch must exist; `--from <base>` forks a missing `--branch` from `<base>` first |
+| `ingest` | deprecated alias of `load --from <base>` (defaults: `--from main --mode merge`); prints a one-line warning to stderr |
 | `query` (alias: `read`) | run named read query; source via `--query <path>`, `-e`/`--query-string <GQ>`, or `--alias <name>` (exactly one). `read` is the deprecated previous name and prints a one-line warning to stderr |
 | `mutate` (alias: `change`) | run mutation query; same `--query` / `-e` / `--alias` mutual-exclusion as `query`. `change` is the deprecated previous name and prints a one-line warning to stderr |
 | `snapshot` | print current snapshot (per-table version + row count) |