fix(grants): add DEFAULT PRIVILEGES for authenticated/anonymous + polling error logging

[pyramation]

Summary

The execution overlay UI was stuck on "executing..." forever because pollExecutionStatus silently caught all GraphQL errors — the catch {} blocks swallowed failures and nsRows stayed empty, causing overallStatus to always evaluate to 'running'.

Two fixes:

1. DEFAULT PRIVILEGES for future tables — constructive_compute_public and constructive_platform_function_graph_public now grant:

   • authenticated: SELECT, INSERT, UPDATE, DELETE on all future tables
   • anonymous: SELECT on all future tables

   This ensures any tables created after the initial GRANT ... ON ALL TABLES still get proper permissions.

2. standalone_schema_access.sql grants for anonymous — adds USAGE + SELECT for the anonymous role on all public schemas. Previously only authenticated had explicit grants; now PostGraphile can serve unauthenticated requests (GraphQL explorer) without permission errors.

3. Error logging in pollExecutionStatus — all three catch blocks now log via console.error so GraphQL failures are visible in browser dev tools:

   } catch (err) {
     console.error('[pollExecutionStatus] node_states query failed:', err);
   }

Root cause analysis: The grants from standalone_schema_access.sql use GRANT ... ON ALL TABLES IN SCHEMA which only covers tables existing at execution time. The ALTER DEFAULT PRIVILEGES ensures tables created afterward (e.g. by future migrations or partition management) are also covered.

Link to Devin session: https://app.devin.ai/sessions/b2291a8e333e445aa125a2efd1996206
Requested by: @pyramation

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