chore(clickhouse): 移除内置 ClickHouse 插件，改走 clickhouse IPC 驱动扩展 - #436

Description

Host-side half of moving ClickHouse onto the extension-driver architecture (same treatment TDengine got when it moved out of the host): the built-in native ClickHouse plugin is removed and DatabaseType::ClickHouse now routes through an IPC external driver with driver_id = "clickhouse".

What changed:

• Removed the built-in plugin: crates/db/src/clickhouse (plugin.rs / connection.rs / codec.rs, ~3.6k lines), the clickhouse dependency in crates/db and the workspace, and the lib module export.
• Routed the type to the external driver: DatabaseType::external_driver_id() maps ClickHouse to Some("clickhouse"), so the connection form, open guard, tree menu and IPC protocol all resolve the extension. DbManager::get_plugin now calls resolve_external_plugin(CLICKHOUSE_IPC_DRIVER_ID); the local compatibility path in ipc/plugin.rs returns None for ClickHouse, exactly like TDengine.
• Legacy connections keep working: required_driver_for_config uses the driver guard, so opening a historical built-in ClickHouse connection prompts to install the extension from the extension market (same policy as DuckDB/TDengine).
• New-connection entry follows the installation: ClickHouse is only listed in the database category when the clickhouse driver is installed (the category already has other members, so no empty-state install row is added).
• Connection form from driver.json: navop_runtime no longer asks the built-in plugin for a ui_manifest; the form is declared by the extension's driver.json.
• Tests rewritten rather than deleted:
  • copy_format: the ClickHouse boolean literal assertion now goes through the external driver's compatible_database_type = ClickHouse and still formats true;
  • table designer DDL sweep excludes types without a native plugin instead of constructing one;
  • the schema-sync FK-ignore case moved to the extension's DDL tests (the host no longer keeps a copy that depends on the removed plugin);
  • added clickhouse_routes_to_external_driver and clickhouse_kind_follows_driver_installation.
• README / README_CN updated.

Dependency before merge

This PR is only useful once the companion extension is published:

• repo: navop-extensions, branch feat/clickhouse-ipc-driver, commit 958cd54 (extensions/ipc/clickhouse, HTTP interface, 25 wire methods, driver.json with compatible_database_type=ClickHouse);
• it is currently published: false and is not yet on the extension market.

Until that extension ships, merging this PR means no ClickHouse support at all: existing ClickHouse connections will show the "install driver" guard. The navop-extensions submodule pointer is intentionally left untouched, matching the TDengine migration, because the driver is delivered through the market rather than bundled.

Break Changes

• ClickHouse no longer ships inside the host binary; it requires the installable clickhouse IPC driver extension. Legacy built-in ClickHouse connections keep their stored config and are routed to the driver by DatabaseType::ClickHouse.
• ClickHouse DDL generation / schema-sync SQL now comes from the extension. Host tests that asserted host-side DDL are removed, not silently skipped — the behavior is covered by the extension's ddl tests.
• Through the HTTP interface the driver has no statement parameter binding: bound parameters return INVALID_PARAMS and affected_rows is reported as 0 rather than fabricated (extension-side detail, listed here so reviewers can see the capability delta).

How to Test

cargo metadata --format-version 1 --locked   # toml/lock consistent
cargo check --workspace --all-targets        # pass
cargo test -p db -p db_view -p main -p navop_runtime

Local results on the rebased branch (base main @ db76dd449):

db:            1320 passed
db_view:        953 passed, 1 ignored
main:           697 passed
navop_runtime:   72 passed (+8 other small targets)

Manual checks:

1. With the clickhouse driver installed: New Connection → database category shows ClickHouse; the form comes from driver.json; connecting and browsing a database works.
2. Without the driver installed: the database category does not list ClickHouse, and opening a previously saved built-in ClickHouse connection shows the install prompt.

Checklist

• I have read the CONTRIBUTING document and followed the guidelines.
• Reviewed the changes in this PR and confirmed AI generated code (If any) is accurate.
• Passed cargo run for story tests related to the changes.
• Tested macOS, Windows and Linux platforms performance (if the change is platform-specific)