feat: add pr, repo, pr_title chat search filters (#25569)

Relates to CODAGT-432

Adds three new search filters to the chat list endpoint (`GET
/api/experimental/chats/`):

- `pr:<number>` - exact PR number match
- `repo:<owner/repo>` - substring match against git remote origin or URL
- `pr_title:<text>` - case-insensitive PR title substring match

Includes SQL filter clauses (EXISTS against `chat_diff_statuses`),
parser with validation, handler wiring, unit tests, swagger annotation
update, and a new search syntax documentation page.

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coderd/searchquery/search.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"fmt"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -553,6 +554,9 @@ func Tasks(ctx context.Context, db database.Store, query string, actorID uuid.UU
 //   - diff_url: string (matches chats whose linked diff URL equals the
 //     given value, case-insensitively; URLs typically contain ':' so
 //     they must be quoted, e.g. q=diff_url:"https://github.com/o/r/pull/1")
+//   - pr: positive integer (exact PR number match)
+//   - repo: string (case-insensitive substring match against git remote origin or URL)
+//   - pr_title: string (case-insensitive PR title substring match)
 func Chats(query string) (database.GetChatsParams, []codersdk.ValidationError) {
 	filter := database.GetChatsParams{
 		// Default to hiding archived chats.
@@ -598,6 +602,21 @@ func Chats(query string) (database.GetChatsParams, []codersdk.ValidationError) {
 	}
 
 	filter.TitleQuery = parser.String(values, "", "title")
+	filter.PrTitleQuery = parser.String(values, "", "pr_title")
+	filter.RepoQuery = parser.String(values, "", "repo")
+
+	// pr: requires a positive integer.
+	if prStr := parser.String(values, "", "pr"); prStr != "" {
+		n, err := strconv.ParseInt(prStr, 10, 32)
+		if err != nil || n <= 0 {
+			parser.Errors = append(parser.Errors, codersdk.ValidationError{
+				Field:  "pr",
+				Detail: fmt.Sprintf("%q is not a valid positive integer", prStr),
+			})
+		} else {
+			filter.PrNumber = int32(n)
+		}
+	}
 
 	parser.ErrorExcessParams(values)
 	return filter, parser.Errors

coderd/searchquery/search_test.go

@@ -1459,6 +1459,55 @@ func TestSearchChats(t *testing.T) {
 				DiffURL:    sql.NullString{String: "https://github.com/coder/coder/pull/456", Valid: true},
 			},
 		},
+		{
+			Name:  "PrNumber",
+			Query: "pr:42",
+			Expected: database.GetChatsParams{
+				Archived: sql.NullBool{Bool: false, Valid: true},
+				PrNumber: 42,
+			},
+		},
+		{
+			Name:                  "PrNumberInvalid",
+			Query:                 "pr:abc",
+			ExpectedErrorContains: "pr",
+		},
+		{
+			Name:                  "PrNumberZero",
+			Query:                 "pr:0",
+			ExpectedErrorContains: "pr",
+		},
+		{
+			Name:                  "PrNumberNegative",
+			Query:                 "pr:-1",
+			ExpectedErrorContains: "pr",
+		},
+		{
+			Name:  "RepoQuery",
+			Query: "repo:coder/coder",
+			Expected: database.GetChatsParams{
+				Archived:  sql.NullBool{Bool: false, Valid: true},
+				RepoQuery: "coder/coder",
+			},
+		},
+		{
+			Name:  "PrTitleQuery",
+			Query: `pr_title:"fix auth bug"`,
+			Expected: database.GetChatsParams{
+				Archived:     sql.NullBool{Bool: false, Valid: true},
+				PrTitleQuery: "fix auth bug",
+			},
+		},
+		{
+			Name:  "CombinedPRRepoTitle",
+			Query: "pr:99 repo:coder/coder pr_title:deploy",
+			Expected: database.GetChatsParams{
+				Archived:     sql.NullBool{Bool: false, Valid: true},
+				PrNumber:     99,
+				RepoQuery:    "coder/coder",
+				PrTitleQuery: "deploy",
+			},
+		},
 		{
 			Name:                  "BareTermsRejected",
 			Query:                 "some random words",