Rename the project spec and update every reference to it

The charter file carried a tool-specific name while being the repository's own
document: mission, non-negotiable constraints, the pinned stack, repo
conventions and phase status, cited as authority by thirty files across the
agent, api, deploy, docs, search and terraform trees.

PROJECT-SPEC.md says what it is. All 42 references are updated in the same
commit, including the relative link in docs/status.md, so nothing points at a
filename that no longer exists.

proto/sentry/logs/v1/logs.proto

@@ -43,7 +43,7 @@ message LogRecord {
 
   // Original, unparsed log line. Always populated, even when structured
   // fields below are also present, per the schema-on-read fallback
-  // requirement in CLAUDE.md.
+  // requirement in PROJECT-SPEC.md.
   string message = 5;
 
   // Structured fields extracted by the agent's parser (e.g. RFC 5424