feat(config): explicit tool routing when multiple LSP servers target the same file extension

[eejd]

Problem

When two [[lsp_servers]] entries share a language_id (or overlapping file_patterns), there is currently no way to specify which server handles which tool calls. This makes it impossible to run complementary servers side-by-side — for example:

• pyright for navigation (get_hover, get_definition, get_references, workspace_symbol_search)
• pylsp for lint diagnostics (get_diagnostics, get_cached_diagnostics) with pycodestyle/flake8/mypy plugins

Both servers target *.py. Today, with two entries present, it is undefined which server responds to any given tool call.

Desired behaviour

A name field on [[lsp_servers]] and a routing table (or per-server handles list) that lets users express which tools are dispatched to which server:

[[lsp_servers]]
name = "pyright"
language_id = "python"
command = "pyright-langserver"
args = ["--stdio"]
file_patterns = ["**/*.py"]
handles = ["hover", "definition", "references", "completions", "workspace_symbols"]

[[lsp_servers]]
name = "pylsp"
language_id = "python"
command = "pylsp"
args = []
file_patterns = ["**/*.py"]
handles = ["diagnostics"]

Alternatively, a [[routing]] top-level section could map tool names → server names for each language.

Use case

Navigation (pyright: full type-aware hover, cross-file definition, workspace symbols) and lint diagnostics (pylsp: pycodestyle, flake8, mypy via plugins) are genuinely complementary. pyright does not expose pycodestyle/flake8 style diagnostics; pylsp's navigation is weaker than pyright's. Being able to pair them in a single mcpls process — without one silently shadowing the other — would make the Python story meaningfully stronger.

Current workaround

Run a separate mcp-language-server (isaacphi) entry alongside mcpls just for pylsp diagnostics. This works but introduces a second bridge process and loses mcpls's single-process TOML model.

Context

• mcpls v0.3.6, macOS arm64
• [[lsp_servers]] TOML fields: language_id, command, args, env, file_patterns, initialization_options, timeout_seconds, heuristics — no name or routing fields currently