Integrate device profiles with SCPI query for automatic connection setup

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Background

Device profiles contain connection settings (baudrate, parity, etc.) and known SCPI commands. Currently, the LLM must manually look up a profile, extract settings, and pass them to serial_query — a multi-step process that wastes context and is error-prone.

Current State

• get_device_profile (handlers.go:479-503) returns profile with Connection struct
• serial_query (handlers.go:417-477) requires all connection params explicitly
• Connection struct (devices.go:27-33) has serial-only fields: baudrate, databits, parity, stopbits, timeout_ms
• No transport field in Connection — assumes serial
• No link between profile lookup and query execution
• LLM workflow: get_device_profile("XDM1241") → extract baudrate, parity, etc. → serial_query(port, cmd, baudrate=115200, ...) — 2 tool calls + manual parameter copying

Problem

• 2 tool calls required where 1 should suffice
• LLM must parse JSON, extract fields, and re-pass them — error-prone
• Connection settings in profile are informational only, not actionable
• No transport type in profile — can't auto-select serial vs TCP
• Extra tool call wastes LLM context tokens

Proposed Changes

1. Add optional device parameter to scpi_query (or serial_query):
   • When provided, auto-lookup device profile from registry
   • Apply profile's connection settings as defaults (baudrate, parity, etc.)
   • Explicitly provided params override profile defaults
2. Add transport field to Connection struct in device profiles:
   • Values: "serial", "tcp", "usbtmc"
   • Default: "serial" for backward compatibility
3. Add optional address field to Connection for TCP devices (host:port)
4. Update device profile JSON schema to include transport info
5. Single-call workflow: scpi_query(device="XDM1241", port="/dev/ttyUSB0", command="*IDN?")
   • Profile provides baudrate, parity, etc. automatically
   • LLM only needs to specify port (physical mapping) and command

Acceptance Criteria

• scpi_query accepts optional device param for auto profile lookup
• Profile connection settings used as defaults when device is specified
• Explicit params override profile defaults
• Connection struct supports transport field
• Device profile JSON schema updated with transport info
• Tests cover: profile-based defaults, explicit override, missing profile fallback
• Single tool call can query a known device with minimal params

Affected Files

• internal/devices/devices.go — add Transport field to Connection
• internal/devices/profiles/*.json — add transport to profiles
• internal/tools/tools.go — add device param to query tool
• internal/tools/handlers.go — profile lookup + merge logic
• internal/tools/handlers_test.go — tests for integrated flow