fix: resolve clippy warnings in lsp module

- Replace map_or(false, ...) with is_none_or(... !=)
- Replace explicit auto-derefs (&*Static) with auto-deref (&Static)
- Refactor range-indexed loop to iterator with enumerate + skip/take
- Suppress deprecated root_path field with allow(deprecated)

docs: update README and REQUIREMENTS for streamd lsp

- Add streamd lsp to commands table in README
- Add Editor Integration section with Zed, Neovim, VS Code snippets
- Add R25 LSP requirements (R25a–R25e) to REQUIREMENTS.md

REQUIREMENTS.md

@@ -400,6 +400,7 @@ Provide recursive search through the shard tree:
 | `streamd edit [n]` | Edit nth file (supports negative indexing for recent files) |
 | `streamd timesheet` | Generate formatted timesheet report with expected/actual hours |
 | `streamd completions <shell>` | Generate shell completions (bash, zsh, fish, elvish, powershell) |
+| `streamd lsp` | Start Language Server Protocol server over stdin/stdout |
 
 ### R21a: Daily Command Behavior
 
@@ -471,3 +472,53 @@ Multiple configurations can be merged:
 - Dimensions are combined (later configs can add new dimensions)
 - Markers are combined (later configs can add new markers)
 - This allows base configuration + domain-specific extensions
+
+---
+
+## LSP Server
+
+### R25: LSP Subcommand
+
+`streamd lsp` starts a Language Server Protocol server over stdin/stdout.
+
+**Workspace root resolution:**
+- The base folder is taken from `initializeParams.rootUri` (or `rootPath` as fallback).
+- R22/R23 global config resolution is bypassed in LSP mode.
+
+**Passive mode:**
+- If `.streamd.toml` is absent from the workspace root, the server enters passive mode: all requests return empty results and no diagnostics are published.
+
+**Config watching:**
+- The server registers a `workspace/didChangeWatchedFiles` watcher for `.streamd.toml`.
+- Config is reloaded without restarting the server when `.streamd.toml` changes.
+
+**Document sync:**
+- Full-document sync (`TextDocumentSyncKind::FULL`).
+- Re-parses on `didOpen`, `didChange`, and `didSave`.
+
+### R25a: LSP Completion
+
+- Trigger character: `@`
+- Returns marker names from the merged config (BasicTimesheetConfiguration + TaskConfiguration).
+- Conditional suggestions: if marker A is on the line and A has placements with `if_with: {B}`, B is offered with higher priority.
+- Temporal snippets: `@` followed by a digit offers `YYYYMMDD` and `HHMMSS` format snippets (R16).
+
+### R25b: LSP Diagnostics
+
+- **File-name format (R15)**: Warning when the file basename does not match `^(\d{8})(?:-(\d{4,6}))?.+\.md$`.
+- **Timesheet violations (R18)**: Error when a day ends without a break; Warning for overlapping timecards.
+
+### R25c: LSP Document Symbols
+
+- Returns the `LocalizedShard` tree as nested `DocumentSymbol` nodes.
+- Symbol names are derived from marker names or tag names.
+
+### R25d: LSP Code Actions
+
+- "Mark task as done": offered on any line containing `@Task` without `@Done`; inserts ` @Done` after `@Task`.
+
+### R25e: LSP Cross-file Features
+
+- `workspace/symbol`: searches all `.md` files in base folder (depth 1) for shards matching the query.
+- `textDocument/references`: finds all occurrences of the `@Marker` under the cursor across the workspace.
+- `textDocument/rename`: renames an `@Marker` across all files via `WorkspaceEdit`.