Bug: /save <path> results in "Session paths are not serialized"

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

Linux 6.1.0-39-amd64 - Debian GNU/Linux 12 (bookworm)

### Expected behaviour

> /context add
> /save -- should save serialized conversation to

### Actual behaviour

> /context add
> /save -- Failed to export to chatservice: Session paths are not serialized

### Steps to reproduce

q chat
> /context add
> /save

### Environment

```yaml

[q-details]
version = "1.15.0"
hash = "a8a0426eaff32ac9b1599ca1b1f1881ffd16054d"
date = "2025-09-02T17:17:19.458949Z (15d ago)"

[system-info]
chip = "Intel(R) Core(TM) i5-3320M CPU @ 2.60GHz"
total-cores = 2
memory = "15.53 GB"

[system-info.os.linux]
kernel_version = "6.1.0-39-amd64"
id = "debian"
name = "Debian GNU/Linux"
pretty_name = "Debian GNU/Linux 12 (bookworm)"
version_id = "12"
version = "12 (bookworm)"

[environment]
cwd = "/home/USER"
cli-path = "/home/USER"
install-method = "unknown"

[env-vars]
DISPLAY = ":0"
PATH = "/home/USER/USER-packages2/protobuf/bin/:/home/USER/USER-packages2/Processing/bin:/home/USER/USER-packages2/tpwriter/bin:/home/USER/USER-packages2/calibre-bin/calibre/bin:/home/USER/USER-packages2/yt-dlp/bin:/home/USER/USER-packages2/picom/bin:/home/USER/.cabal/bin:/home/USER/.ghcup/bin:/home/USER/.cargo/bin:/home/USER/USER-packages2/gdb16/bin:/home/USER/USER-packages2/clangd/bin:/home/USER/USER-packages2/coursier:/home/USER/USER-packages2/kls/bin:/home/USER/.nvm/versions/node/v22.14.0/bin:/home/USER/.sdkman/candidates/scala/current/bin:/home/USER/.sdkman/candidates/sbt/current/bin:/home/USER/.sdkman/candidates/kotlin/current/bin:/home/USER/.sdkman/candidates/java/current/bin:/home/USER/.sdkman/candidates/gradle/current/bin:/home/USER/USER-packages/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/home/USER/.local/bin:/home/USER/USER-packages2/go/bin:/home/USER/go/bin:/home/USER/.local/bin:/home/USER/USER-packages2/dotnet:/home/USER/.dotnet/tools"
QTERM_SESSION_ID = "8305218316e0446c88978bb7aaa622a5"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.15.0"
SHELL = "/bin/bash"
TERM = "xterm-256color"
XDG_CURRENT_DESKTOP = "i3"
XDG_SESSION_DESKTOP = "i3"
XDG_SESSION_TYPE = "x11"
```