feat(rain): add Ignore() support to InsertQuery

[cungminh2710]

This PR implements the .Ignore() method for the InsertQuery builder, bringing Rain ORM closer to feature parity with Drizzle ORM.

Key changes:

• Added Ignore() method to InsertQuery.
• Refactored INSERT INTO rendering to support dialect-specific ignore prefixes (INSERT IGNORE for MySQL, INSERT OR IGNORE for SQLite).
• Updated PostgreSQL rendering to use ON CONFLICT DO NOTHING when ignore is requested.
• Unified Ignore() with targetless OnConflict().DoNothing() calls using a new internal useIgnore() helper.
• Added comprehensive unit tests for all supported dialects and insert variations (values, select, default values).
• Updated existing MySQL tests to use the new idiomatic syntax.

Feature parity target: Drizzle's .ignore() and targetless onConflictDoNothing() behavior.

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PR created automatically by Jules for task 4831643794802559569 started by @cungminh2710

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[greptile-apps]

Greptile Summary

This PR adds ignore support for insert queries. The main changes are:

• New InsertQuery.Ignore() builder method.
• Dialect-specific ignore SQL for PostgreSQL, MySQL, and SQLite.
• Targetless OnConflict().DoNothing() mapped to ignore-style SQL.
• New SQL rendering tests for ignore insert variants.

Confidence Score: 4/5

Explicit conflict clauses can be dropped when they are chained with Ignore().

• MySQL and SQLite can skip requested DoUpdateSet clauses.
• PostgreSQL can turn a targetless update conflict into DO NOTHING.
• The simple ignore paths are covered by tests, but mixed builder chains need fixes.

pkg/rain/query_insert.go

Important Files Changed

Filename	Overview
pkg/rain/query_insert.go	Adds the ignore flag and dialect rendering, but the helper treats Ignore() as overriding explicit conflict clauses.
pkg/rain/query_insert_ignore_test.go	Adds coverage for simple ignore inserts and targetless do-nothing behavior across dialects.
pkg/rain/query_insert_test.go	Updates MySQL targetless do-nothing expectations to use native ignore syntax.

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
pkg/rain/query_insert.go:289-291
**Ignore Overrides Explicit Conflict**

When a caller chains `Ignore()` with an explicit conflict rule, `useIgnore()` returns true from `q.ignore` before looking at the configured conflict action. On MySQL and SQLite this makes `writeConflictClause` skip the conflict clause, so `.Ignore().OnConflict(users.Email).DoUpdateSet(users.Name)` emits only `INSERT IGNORE` or `INSERT OR IGNORE` and silently drops the requested update.

### Issue 2 of 2
pkg/rain/query_insert.go:872-875
**Targetless Update Becomes DoNothing**

With PostgreSQL, `.Ignore().OnConflict().DoUpdateSet(...)` reaches this block with `useIgnore()` true from `q.ignore` and no conflict target. The code emits `ON CONFLICT DO NOTHING`, so the requested update assignments are discarded instead of returning the existing target-required error.

_{Reviews (1): Last reviewed commit: "feat(rain): add Ignore() support to Inse..." | Re-trigger Greptile}

[greptile-apps]

Ignore Overrides Explicit Conflict

When a caller chains Ignore() with an explicit conflict rule, useIgnore() returns true from q.ignore before looking at the configured conflict action. On MySQL and SQLite this makes writeConflictClause skip the conflict clause, so .Ignore().OnConflict(users.Email).DoUpdateSet(users.Name) emits only INSERT IGNORE or INSERT OR IGNORE and silently drops the requested update.

Prompt To Fix With AI

This is a comment left during a code review.
Path: pkg/rain/query_insert.go
Line: 289-291

Comment:
**Ignore Overrides Explicit Conflict**

When a caller chains `Ignore()` with an explicit conflict rule, `useIgnore()` returns true from `q.ignore` before looking at the configured conflict action. On MySQL and SQLite this makes `writeConflictClause` skip the conflict clause, so `.Ignore().OnConflict(users.Email).DoUpdateSet(users.Name)` emits only `INSERT IGNORE` or `INSERT OR IGNORE` and silently drops the requested update.

How can I resolve this? If you propose a fix, please make it concise.

[greptile-apps]

Targetless Update Becomes DoNothing

With PostgreSQL, .Ignore().OnConflict().DoUpdateSet(...) reaches this block with useIgnore() true from q.ignore and no conflict target. The code emits ON CONFLICT DO NOTHING, so the requested update assignments are discarded instead of returning the existing target-required error.

Prompt To Fix With AI

This is a comment left during a code review.
Path: pkg/rain/query_insert.go
Line: 872-875

Comment:
**Targetless Update Becomes DoNothing**

With PostgreSQL, `.Ignore().OnConflict().DoUpdateSet(...)` reaches this block with `useIgnore()` true from `q.ignore` and no conflict target. The code emits `ON CONFLICT DO NOTHING`, so the requested update assignments are discarded instead of returning the existing target-required error.

How can I resolve this? If you propose a fix, please make it concise.