feat(docs): man pages for gasm and every command, guarded against CLI drift

Assisted-by: GLM 5.3 Flash

docs/man/gasm-lsp.1

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+.TH GASM-LSP 1 "2026-09-19" "gasm 0.33.0" "User Commands"
+.SH NAME
+gasm-lsp \- run the Plan 9 assembly language server
+.SH SYNOPSIS
+.B gasm lsp
+.SH DESCRIPTION
+Run the language server over standard input/output: JSON-RPC 2.0 with
+Content-Length framing.  Point an LSP-capable editor at the binary and
+associate it with
+.I .s
+files; the target architecture is inferred from the file suffix
+(_amd64.s, _arm64.s, _riscv64.s, _loong64.s).
+.PP
+Provides completion, hover, document symbols, push and pull
+diagnostics, semantic-token highlighting, go-to-definition, find
+references, rename, formatting, inlay hints, code actions, signature
+help, document highlights, workspace symbol search, include document
+links and folding ranges; definition, references and rename work across
+every open document.  Syntax highlighting is delivered as LSP semantic
+tokens, so no editor-specific grammar is required.
+.SH EXIT STATUS
+Runs until the client closes the session; exits 0 on a clean shutdown.
+.SH SEE ALSO
+.BR gasm (1)