Docs: marketplace, and clean up new-code warnings/lints

CLAUDE.md gets a Marketplace subsection under Key Conventions (the sync
script is app-embedded and re-uploaded on every sync, never baked into
container/ — pre-flight F9) and the Settings export/import section now
covers marketplace account tokens traveling in ExportedSecrets and the
import preview's warning on global hook and plugin installs.
HOW-TO-USE.md gets a Marketplace section (placed after Shared Claude
Authentication) with its Table of Contents entry (pre-flight N13). The
spec doc's stale keychain service name, gh-login flags and
upload_bytes_to_container signature are amended to match the shipped
code (pre-flight N10).

Also fixes the new marketplace code's remaining build/clippy warnings:
BTreeMap/Sha256/Digest imports in tree.rs gated behind #[cfg(test)]
(their only uses are on MemTree, already test-only), the unused
`pub use marketplace::*` glob re-export dropped from models/mod.rs,
gh_login::strip_ansi marked #[cfg(test)] (production streams through
AnsiStripper instead), and four clippy lints in marketplace test code
(double_ended_iterator_last, cloned_ref_to_slice_refs x2,
single_match). Flushes the unresolved getMarketplaceSyncReport promise
in MarketplaceSection.test.tsx's "opens the Marketplace filtered to
this project" test to remove its act() warning.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/src-tauri/src/marketplace/auth.rs

@@ -641,12 +641,12 @@ mod tests {
 
         // And the target must never see a connection carrying the token —
         // ideally no connection at all, since the client never follows.
-        match rx.recv_timeout(StdDuration::from_millis(500)) {
-            Ok(request) => assert!(
+        // no connection at all is also the expected outcome
+        if let Ok(request) = rx.recv_timeout(StdDuration::from_millis(500)) {
+            assert!(
                 !request.contains(FAKE) && !request.to_ascii_lowercase().contains("private-token"),
                 "the redirect target must never receive the token: {request}"
-            ),
-            Err(_) => {} // no connection at all — the expected outcome
+            );
         }
     }
 }

app/src-tauri/src/marketplace/gh_login.rs

@@ -67,8 +67,9 @@ pub fn valid_host(host: &str) -> bool {
 /// Remove terminal control sequences and carriage returns from one complete
 /// piece of text. An unterminated sequence at the end is dropped. The login
 /// itself uses a streaming [`AnsiStripper`], which carries a sequence split
-/// across chunks instead.
-pub fn strip_ansi(s: &str) -> String {
+/// across chunks instead; this one-shot form exists for tests only.
+#[cfg(test)]
+fn strip_ansi(s: &str) -> String {
     AnsiStripper::default().push(s.as_bytes())
 }
 

app/src-tauri/src/marketplace/git.rs

@@ -91,7 +91,7 @@ pub fn classify_fetch_error(chain: &str) -> FetchError {
         let cause = chain
             .lines()
             .filter_map(|l| l.trim_start().strip_prefix("└─"))
-            .last()
+            .next_back()
             .unwrap_or(chain);
         return FetchError::Network(first_line(cause));
     }
@@ -600,7 +600,7 @@ mod tests {
         want.sort();
         assert_eq!(pins(&repo), want);
 
-        set_pins(&repo, &[b.clone()]).unwrap();
+        set_pins(&repo, std::slice::from_ref(&b)).unwrap();
         assert_eq!(pins(&repo), vec![format!("{}{}", PIN_PREFIX, b)]);
     }
 

app/src-tauri/src/marketplace/sync.rs

@@ -241,7 +241,7 @@ mod tests {
             skipped: vec![script_skip.clone()],
             ..Default::default()
         };
-        let merged = with_payload_skips(report, &[payload_skip.clone()]);
+        let merged = with_payload_skips(report, std::slice::from_ref(&payload_skip));
         assert_eq!(merged.skipped, vec![payload_skip, script_skip]);
     }
 

app/src-tauri/src/marketplace/tree.rs

@@ -4,8 +4,10 @@
 //! against [`MemTree`] with no git involved, and runs in production against
 //! [`GitTree`], which reads git objects straight out of the bare cache.
 
+#[cfg(test)]
 use std::collections::BTreeMap;
 
+#[cfg(test)]
 use sha2::{Digest, Sha256};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]