feat: add SELECT statement for retrieving a point by ID

[srimon12]

Summary

This PR adds first-class point retrieval by ID to QQL with a strict, minimal SQL-like syntax:

SELECT * FROM <collection> WHERE id = '<point_id>'
SELECT * FROM <collection> WHERE id = <integer_id>

The scope is intentionally narrow for safety and clarity:

• only * projection is supported
• only WHERE id = ... is supported

Why

QQL already supports insert/search/recommend/delete, but lacked a direct read-by-ID operation.
Qdrant SDK already provides retrieve(...), so this closes a real CRUD gap with low implementation risk.

Changes

• Lexer:

  • add SELECT keyword token
  • add * token (STAR)

• Parser:

  • add SELECT * FROM <collection> WHERE id = <string|integer> statement parsing
  • add strict validation for point-id value type
  • reuse point-id parsing helper for both SELECT and DELETE id paths

• AST:

  • add SelectStmt(collection, point_id)

• Executor:

  • execute SelectStmt via QdrantClient.retrieve(...)
  • return payload-only result shape:
    • found: {"id": "<id>", "payload": {...}}
    • not found: success message with data=None
  • raise clear runtime errors for non-existent collections and SDK failures

• Script runner:

  • include SELECT in top-level statement split starters

• CLI:

  • add SELECT syntax to help text
  • add pretty-print table for single SELECT result

• Docs:

  • add SELECT syntax/examples and constraints
  • update reference/error docs from “SELECT unsupported” to supported strict form
  • update quick syntax/programmatic docs
  • update test-count badges/text to current suite total

Tests

Added/updated tests for:

• lexer tokenization of SELECT and *
• parser success and strict-scope rejection cases
• executor behavior:
  • found record
  • not found
  • missing collection
• script statement splitting with SELECT

Full test run:

• pytest -q
• result: 414 passed