feat: honor optional Posts.IsActive and Notes.IsActive

Both columns carry the meaning Blogs.IsActive has: 0 = removed by another
tool, anything else (including NULL) = live. Neither exists in the live
TL.db yet, and both are added from outside this crawler, so the code has
to work on databases either side of the change - naming a missing column
is a hard SQLite error.

HasIsActiveColumn asks PRAGMA table_info once per table per database path
and caches it; AndIsActive/WhereIsActive return "COALESCE(IsActive, 1) = 1"
or an empty string. Every read that selects posts or notes now carries the
filter: GetPosts (both branches, including the per-blog count subquery),
GetReplies, GetRepliesWithMissingText, GetRepliesWithFilledText,
GetAllPostTextColumns, GetAllPostsForBlog, GetPost, GetPostByIdAnyBlog,
and the engagement queries that count or join Notes - GetBlogs,
GetBlogsAll and both note-joining variants of GetBlogsForLikes.

The LEFT JOIN Notes in GetPosts is left alone on purpose: nothing is
selected from it and it can neither add nor remove a row.
LegacyPostsDbImporter is left alone too - it reads a foreign legacy
schema.

Writes were already safe and are documented rather than changed: no
INSERT column list names IsActive, no UPDATE sets it, MapPrefixToColumn
cannot map to it, and there is no INSERT OR REPLACE on Posts or Notes for
a column default to be reset by. Re-crawling a removed row refreshes its
content and leaves the flag at 0. As with Blogs, exclusion belongs at
selection, so the update paths stay keyed on rows the caller already
chose.

Verified against three synthetic databases - no IsActive columns, columns
present with a removed post and its notes, and columns present but NULL -
by running every affected reader: the queries are valid in all three, the
removed rows drop out only where the columns exist, NULL reads as live,
and AddPost/AddNote/UpsertPostFromTextFile/UpdatePostContentFields leave
an IsActive = 0 row at 0.

Co-Authored-By: Claude Opus 5 <[email protected]>

verify-db-schema.sql

@@ -142,6 +142,9 @@ ORDER BY et.tbl;
 -- 1c. EXTRA / UNEXPECTED COLUMNS: present in the DB but not in the expected
 --     list above. Informational only -- e.g. a NEWER backup, or a column this
 --     script's expected-list hasn't been updated for. Not an error by itself.
+--     Posts.IsActive and Notes.IsActive are listed here and NOT in 1a on
+--     purpose: they are written by other tools, the app only reads them when
+--     present, and it must not be told to add them. See TL.db.md.
 WITH expected(tbl, col) AS (
   VALUES
     ('Posts','BlogName'),('Posts','PostID'),('Posts','HasNotesGathered'),('Posts','reblogURL'),
@@ -150,14 +153,14 @@ WITH expected(tbl, col) AS (
     ('Posts','Quote'),('Posts','Body'),('Posts','Tags'),('Posts','Link'),('Posts','PhotoURL'),
     ('Posts','PhotoCaption'),('Posts','DownloadedFiles'),('Posts','AudioCaption'),('Posts','Question'),
     ('Posts','Answer'),('Posts','Title'),('Posts','ByLikes'),('Posts','RootBlogName'),('Posts','RootURL'),
-    ('Posts','DateModified'),('Posts','DateCreated'),('Posts','PostType'),
+    ('Posts','DateModified'),('Posts','DateCreated'),('Posts','PostType'),('Posts','IsActive'),
     ('Blogs','BlogName'),('Blogs','HasBeenOutput'),('Blogs','IsActive'),('Blogs','DateAdded'),
     ('Blogs','ByLikes'),('Blogs','DateModified'),('Blogs','DateCreated'),('Blogs','LikesPulled'),
     ('Blogs','LikesCursor'),('Blogs','LikesNewestTimestamp'),('Blogs','LikesLastRefreshed'),
     ('Blogs','LikesLastNewCount'),('Blogs','TTFolderPath'),
     ('Notes','RootBlogName'),('Notes','PostID'),('Notes','NoteBlogName'),('Notes','TimeStamp'),
     ('Notes','Type'),('Notes','DatetimeCrawled'),('Notes','DateModified'),('Notes','DateCreated'),
-    ('Notes','replyText'),
+    ('Notes','replyText'),('Notes','IsActive'),
     ('DailyAPICount','Date'),('DailyAPICount','APICount'),
     ('ApiKeyPoolState','KeyName'),('ApiKeyPoolState','RetryUntil'),
     ('ApiKeyPoolMeta','Id'),('ApiKeyPoolMeta','LastIndex')