fix: remove If-Match header and stop clearing storage on 412

[kptdobe]

Problem

persistence.put sent If-Match: * on every PUT to da-admin. This header tells da-admin "only apply this write if the resource already exists." When the document didn't exist yet (new document, DO cold-start before the first successful write), da-admin returned 412 Precondition Failed.

The 412 handler then:

1. Called ydoc.storage.deleteAll() — destroying the entire Yjs state, including images not yet flushed to da-admin
2. Closed all WebSocket connections — forcing all clients to reconnect and reload from a now-empty da-admin

This was the chain that caused inserted images to permanently disappear.

Root cause

If-Match: * has no useful purpose in the collab context:

• Collab is the authoritative writer for a document once a session is open
• Whether the resource already exists in da-admin or not, the PUT should always proceed
• The syncadmin/deleteadmin APIs are the correct mechanism for coordinating external changes

Solution

• Remove If-Match: * from persistence.put — da-admin now always accepts PUT unconditionally
• Remove the 412 special-case handler — a 412 (or any other non-2xx) is now treated like any other PUT failure: log the error, surface it via the ydoc error map, and return the current content so the debounced save can retry on the next edit
• Only 401/403 still trigger session termination (genuine auth failures)

Tests

• Two new tests assert the correct behavior: If-Match header is absent on PUT; 412 does NOT clear storage or close connections
• Test persistence update shows error but preserves state on 412 replaces the old "closes all and cleans storage" test
• Four existing put tests updated: If-Match: * assertions replaced with null assertions

🤖 Generated with Claude Code

[bosschaert]

I think the If-Match header was added to fix a specific issue: b33ae65

@karlpauls could you please review?

[kptdobe]

Closing — root cause is in da-admin, not da-collab

After deeper analysis, the root cause of the image loss is a bug in da-admin's If-Match: * handling, not in da-collab's use of the header. Removing If-Match: * from da-collab would regress the intentional no-implicit-creation capability introduced by #105.

What actually happens

When da-collab sends PUT with If-Match: *, da-admin correctly validates that the document exists (returning 412 only when current.status === 404). However, it then uses the document's current ETag for the actual R2 write (If-Match: <etag>). If a concurrent write (e.g. during a DO live migration) changes the ETag between the existence check and the write, R2 rejects the PUT with 412.

At that point da-admin has two paths:

• No client conditional → retry transparently (fetches fresh ETag and tries again)
• Client sent If-Match → return 412 immediately without retry

The second path conflates If-Match: * (wildcard — "document must exist") with If-Match: "<specific-etag>" (version lock — "document must have this exact version"). A wildcard should behave like the no-conditional path on ETag mismatch because the document still exists; only a specific ETag warrants a non-retriable 412.

The fix

da-admin PR to follow — putObjectWithVersion retries on R2 ETag mismatch when If-Match: * was sent, exactly as it does for internal (no-conditional) writes. If-Match: "<specific-etag>" still returns 412 without retry.

da-collab: no changes needed.