fix(github): reject a fractional comment line instead of truncating it

toLineNumber ran Math.trunc, so line 3.9 posted the review comment on line 3 —
a silent change to what the caller asked for, on a field where landing on the
wrong line of the diff is invisible until someone reads the comment. A
non-integer now fails with a message naming the field, matching how a missing
head commit SHA fails on this path. Blank and unparseable input is still
omitted: line is optional and nothing usable was supplied.

Author: waleedlatif1

apps/sim/tools/github/comment.test.ts

@@ -286,6 +286,44 @@ describe('github_comment line coercion', () => {
     expect(calls()[1].body).toMatchObject({ line: 42 })
   })
 
+  it('keeps an integer line typed with surrounding whitespace', async () => {
+    secureGitHubRequest.mockResolvedValueOnce(createdCommentResponse())
+
+    await commentTool.directExecution!({
+      ...FILE_COMMENT_PARAMS,
+      commitId: OTHER_SHA,
+      line: '  42  ' as unknown as number,
+    })
+
+    expect(calls()[0].body).toMatchObject({ line: 42 })
+  })
+
+  it('rejects a fractional line rather than silently moving the comment', async () => {
+    secureGitHubRequest.mockResolvedValueOnce(createdCommentResponse())
+
+    await expect(
+      commentTool.directExecution!({
+        ...FILE_COMMENT_PARAMS,
+        commitId: OTHER_SHA,
+        line: 3.9,
+      })
+    ).rejects.toThrow('GitHub line numbers are whole numbers, but line was 3.9')
+    expect(secureGitHubRequest).not.toHaveBeenCalled()
+  })
+
+  it('rejects a fractional line typed into the short input', async () => {
+    secureGitHubRequest.mockResolvedValueOnce(createdCommentResponse())
+
+    await expect(
+      commentTool.directExecution!({
+        ...FILE_COMMENT_PARAMS,
+        commitId: OTHER_SHA,
+        line: '3.9' as unknown as number,
+      })
+    ).rejects.toThrow('GitHub line numbers are whole numbers, but line was 3.9')
+    expect(secureGitHubRequest).not.toHaveBeenCalled()
+  })
+
   it('omits a blank or unparseable line rather than sending NaN', async () => {
     for (const line of ['', '   ', 'abc', undefined, null]) {
       secureGitHubRequest.mockReset()

apps/sim/tools/github/comment.ts

@@ -64,14 +64,30 @@ function needsCommitLookup(params: CreateCommentParams): boolean {
 
 /**
  * The block renders `line` as a short input, so a typed line number reaches the tool
- * as a string while GitHub types the field as an integer. Anything that is not a
- * finite number is omitted rather than sent as `NaN`.
+ * as a string while GitHub types the field as an integer. Blank and unparseable input
+ * is omitted rather than sent as `NaN` — `line` is optional, and nothing usable was
+ * supplied.
+ *
+ * A fractional value is rejected instead of truncated. `3.9` is not the caller asking
+ * for line 3, and quietly posting the review comment on a different line of the diff
+ * than the one they named is the failure they would never think to look for. This
+ * fails the way a missing head commit SHA does: loudly, naming what to set.
  */
 function toLineNumber(value: unknown): number | undefined {
-  if (typeof value === 'number') return Number.isFinite(value) ? Math.trunc(value) : undefined
-  if (typeof value !== 'string' || !value.trim()) return undefined
-  const parsed = Number(value.trim())
-  return Number.isFinite(parsed) ? Math.trunc(parsed) : undefined
+  let parsed: number
+  if (typeof value === 'number') {
+    parsed = value
+  } else {
+    if (typeof value !== 'string' || !value.trim()) return undefined
+    parsed = Number(value.trim())
+  }
+  if (!Number.isFinite(parsed)) return undefined
+  if (!Number.isInteger(parsed)) {
+    throw new Error(
+      `GitHub line numbers are whole numbers, but line was ${parsed}. Set line to the integer line number in the diff.`
+    )
+  }
+  return parsed
 }
 
 function fileCommentBody(