Refresh docs: remove PROCESS.md, fix snapshot ID format, document pre-1.0 migration policy

AGENTS.md

@@ -38,10 +38,9 @@ Version: 2025-06-08
 1. Before committing, tests must pass (`make test`), linting must pass
    (`make lint`), and code must be formatted (`make fmt`).  For go, those
    makefile targets should use `go fmt` and `go test -v ./...` and
-   `golangci-lint run`.  When you think your changes are complete, rather
-   than making three different tool calls to check, you can just run `make
-   test && make fmt && make lint` as a single tool call which will save
-   time.
+   `golangci-lint run`.  Each Makefile target does exactly one thing — to
+   run lint + fmt-check + test together (the standard pre-commit gate),
+   use `make check`.
 
 2. Always write a `Makefile` with the default target being `test`, and with
    a `fmt` target that formats the code.  The `test` target should run all
@@ -103,3 +102,9 @@ Version: 2025-06-08
     build files are acceptable in the root, but source code and other files
     should be organized in appropriate subdirectories.
 
+13. Pre-1.0: NEVER write database migrations. There are no live databases
+    anywhere — every user's local index can be rebuilt from a fresh full
+    backup. When the schema changes, just change `schema.sql` (and any code
+    that touches the affected tables). The local index is disposable until
+    1.0 ships and is tagged.
+