Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@cmd/apply/apply.go`:
- Around line 236-241: The deferred call to sshAgent.Stop() may panic when
sshUtils.NewAgentManager(log) returns an error and sshAgent is nil; update the
code to only defer sshAgent.Stop() when sshAgent is non-nil (e.g., check the
result of sshUtils.NewAgentManager and, after ensuring err == nil and sshAgent
!= nil, register defer sshAgent.Stop()), or assign sshAgent to a local variable
and use a nil-check inside the deferred closure before calling Stop(); reference
sshAgent, sshUtils.NewAgentManager, and Stop() when making the change.

In `@internal/ssh/agent.go`:
- Around line 312-319: The code calls os.Stat(tmpdir) and if it returns
os.ErrNotExist it creates the dir with os.MkdirAll(tmpdir, 0o777|os.ModeSticky)
but then still returns the original stat error unconditionally; update the
branch so that when errors.Is(err, os.ErrNotExist) and os.MkdirAll succeeds you
do NOT return the original err (only return on MkdirAll failure or other
non-NotExist stat errors). Locate the tmpdir check around os.Stat and
os.MkdirAll and remove or guard the final return "", err so success paths
continue normally.
- Around line 242-243: The goroutine passed to s.wg.Go (e.g., the callback that
currently defers s.wg.Done() around s.acceptConnections and the handler at the
shown callback at lines 296–299) is calling Done() manually even though
WaitGroup.Go automatically handles Done(); remove the manual defer s.wg.Done()
from any functions or anonymous goroutines supplied to s.wg.Go (leave the
callsites like s.wg.Go(s.acceptConnections) or the anonymous callback intact),
ensuring Done() is only called by WaitGroup.Go to avoid a double Done/underflow
panic.

In `@internal/system/ssh.go`:
- Around line 100-116: The current logic only uses PrivateKeyCmd output when
options.AgentManager is present, causing key-based auth to be dropped if
AgentManager is nil or manager.Add fails; change the flow in the block around
options.PrivateKeyCmd/runPrivateKeyCmd so that after obtaining privateKey (or
its bytes) you attempt to add it to the agent if manager != nil and manager.Add
succeeds, but regardless of agent availability or Add failure, parse the
returned private key into an ssh.Signer (use the same conversion that
runPrivateKeyCmd returns) and append a direct key auth method to auth (e.g.,
ssh.PublicKeys with the signer or equivalent), while keeping the existing
ssh.PublicKeysCallback(manager.Client().Signers) when manager is present and Add
succeeded; reference options.PrivateKeyCmd, runPrivateKeyCmd, manager.Add, auth,
and ssh.PublicKeysCallback to locate where to add the fallback signer append.
- Around line 164-166: The code appends a possibly relative path when
os.UserHomeDir() fails; change the block in internal/system/ssh.go so you check
the error and the returned homeDir before building knownHostsUserFile and
appending to defaultKnownHosts (i.e., only construct filepath.Join(homeDir,
".ssh", "known_hosts") and append it when err == nil and homeDir != "");
optionally fall back to HOME env or log/skipped addition when the home directory
can't be determined to avoid writing a known_hosts file into the current working
directory.

---

Outside diff comments:
In `@internal/system/ssh.go`:
- Around line 256-260: The code currently sets s.sudoPassword = bytePassword
before verification, causing an unverified password to be cached; move the
assignment so s.sudoPassword is only set after testRemoteRoot succeeds, or if
you prefer to keep the assignment where it is, ensure you clear it on error
(e.g., set s.sudoPassword = nil) when testRemoteRoot(rootCmd) returns an error;
update the block around testRemoteRoot, referencing s.sudoPassword,
testRemoteRoot, rootCmd, and bytePassword accordingly.

---

Nitpick comments:
In `@internal/system/ssh.go`:
- Around line 296-297: The Clone implementation currently assigns the
sudoPassword slice by reference (sudoPassword: s.sudoPassword), which shares the
backing array across clones; change Clone (or the method constructing the cloned
ssh session) to deep-copy the password bytes: if s.sudoPassword != nil create a
new []byte of the same length, copy the contents, and assign that new slice to
sudoPassword (handle nil appropriately) so each clone has its own backing array.