fix(connection-form): show the right default socket path per database type (#1902)

[datlechin]

Fixes #1902.

Problem

In the New/Edit Connection form, when SSH tunneling is enabled the Socket Path field showed the same PostgreSQL hint (/var/run/postgresql/.s.PGSQL.5432) for every database type, so MySQL and MariaDB connections got the wrong default.

Root cause

GeneralPaneView.swift hardcoded the field's placeholder to the PostgreSQL socket regardless of type. It is hint text only, never a saved value, so no stored connections were affected.

Fix

Route the placeholder through the existing per-type metadata system instead of hardcoding it, so it is correct for every driver. Same plumbing as defaultPort and hidesBuiltInPassword, entirely app-side: PluginMetadataSnapshot.ConnectionConfig is an internal app struct, not a PluginKit transfer type, so there is no PluginKit ABI bump and no plugin re-release.

• Added defaultUnixSocketPath to ConnectionConfig.
• Seeded MySQL / MariaDB → /var/run/mysqld/mysqld.sock, PostgreSQL → /var/run/postgresql/.s.PGSQL.5432, Redis → /var/run/redis/redis.sock.
• Preserved the value in buildMetadataSnapshot so a loading plugin binary can't drop it (same pattern as hidesBuiltInPassword).
• Added PluginManager.defaultUnixSocketPath(for:) and a NetworkPaneViewModel.socketPathPrompt computed property that falls back to a generic /path/to/database.sock for types with no socket convention.
• Bound the field's prompt to socketPathPrompt.

The values match TablePro's own docs table in docs/databases/ssh-tunneling.mdx, so no docs change was needed.

Tests

• SocketPathPlaceholderTests — defaultUnixSocketPath(for:) returns the right path for MySQL, MariaDB, PostgreSQL, and Redis, and nil for SQLite, ClickHouse, and unknown types.
• Extended NetworkPaneSocketForwardTests — socketPathPrompt follows the database type and falls back to the generic hint for a socketless type.

Notes

• No new UI test: the sibling per-type placeholders (filePathPrompt, containerEntityPlaceholder) are covered at the metadata/view-model layer, not with UI automation, and this follows the same pattern.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Use the concrete type for socket path metadata

When the connection form is opened for a PostgreSQL-backed alias such as Redshift or CockroachDB, databaseType.pluginTypeId resolves to PostgreSQL via the registry aliases, so this lookup returns /var/run/postgresql/.s.PGSQL.5432 even though those concrete snapshots do not define a Unix-socket convention. That leaves the new per-type placeholder wrong for those database types; this UI metadata should be read from the concrete type snapshot instead of the driver lookup ID.

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