feat: add pcm_update_save tool for writing changes to a new .cdb file

[mpicciolli]

Summary

Adds a new pcm_update_save MCP tool that runs a single write statement (INSERT/UPDATE/DELETE) against a Pro Cycling Manager .cdb save and serializes the result to a new .cdb file. The source save is never modified.

What's new

• pcm_update_save tool (src/tools/update-save.ts) — executes exactly one data-mutating statement and writes the edited database to outputPath (which must differ from savePath). Returns outputPath, rowsModified, and the normalized statement. SELECT, DDL (DROP/CREATE/ALTER), and stacked statements are rejected.
• Write path in save-db.ts — withSaveDb gains an opt-in { queryOnly: false } config; a new writeSaveDb helper re-encodes the sql.js database to PCM's compressed .cdb format via sqlToCdb and refuses to overwrite the source save.
• Shared SQL helpers (src/helpers.ts) — extracted parseSingleStatement (statement normalization + single-statement enforcement using sql-query-identifier, so a ; inside a string literal isn't mistaken for a separator) and explainQueryError (actionable messages for missing table/column and read-only violations). Both are now shared by the read and write tools, and pcm_query_save was refactored to reuse them.

Safety

• The source .cdb is only ever read; writes always go to a separate output file.
• writeSaveDb throws if outputPath isn't a .cdb or resolves to the source path.
• Only a single INSERT/UPDATE/DELETE is allowed — schema changes are blocked to keep the sqlToCdb round-trip intact.

[Copilot]

Pull request overview

This PR introduces the first write-capable MCP tool in the repo (pcm_update_save) to apply a single INSERT/UPDATE/DELETE to an in-memory PCM save DB and serialize the result to a separate .cdb file, while refactoring shared SQL parsing/error-mapping helpers and updating documentation accordingly.

Changes:

• Added pcm_update_save tool with single-statement write enforcement and output serialization.
• Refactored pcm_query_save to reuse shared parseSingleStatement + explainQueryError helpers.
• Extended withSaveDb with an opt-in write mode and added writeSaveDb, plus added vitest coverage and README updates.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/tools/update-save.test.ts	Adds vitest coverage for pcm_update_save behavior and statement validation.
src/tools/update-save.ts	Implements and registers the new pcm_update_save MCP tool and assertWriteStatement.
src/tools/query-save.ts	Refactors query parsing/error handling to shared helper utilities.
src/tools/index.ts	Registers the new tool in the server tool registry.
src/save-db.ts	Adds opt-in write mode to withSaveDb and introduces writeSaveDb for .cdb serialization.
src/helpers.ts	Adds shared parseSingleStatement and explainQueryError.
README.md	Updates readme to describe the new guarded write tool and revised safety story.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.