Fix .my_name resolution and add source(self) annotation for beliefs

[mrebollo]

Summary

This PR fixes .my_name resolution in agentspeak/stdlib.py, adds source(self) annotations for beliefs created without an explicit source in agentspeak/runtime.py, and enables the counting example for runtime validation.

Changes

• Update .my_name unification to use str(agent.name) instead of Literal(agent.name).
• Add source(self) automatically when a belief is inserted without an existing source(...) annotation.
• Enable .my_name usage in examples/counting/counting.asl so the example prints the agent name at the end of counting.

Why

These changes improve consistency in two areas:

• .my_name should unify with a plain string value.
• beliefs inserted locally without a source should carry source(self) so their origin is explicit and consistent with message-based beliefs.

Validation

Validated locally by running:

• pytest -q tests/test_stdlib.py tests/test_terms.py tests/test_parser.py
• python -m agentspeak examples/counting/counting.asl

The test suite passed, and the counting example printed the resolved agent name correctly.

Scope

This PR is limited to python-agentspeak changes related to:

• .my_name resolution
• automatic source(self) annotation for beliefs
• example-level validation in examples/counting/counting.asl