Implement Traits to Simplify Code in promptforge-api-types

[seanpar203]

What was done

I implemented several traits for the Timestamp, this allows to simplify the code and do things like Timestamp::now() and it will automatically pull the system epoch time instead of how it was before.

And some similar simplifications to other things like ToolId andCapabilityId.

Before & After TimeStamp

Before

// Manual boilerplate in every caller that records timestamps:
let timestamp = SystemTime::now()
    .duration_since(UNIX_EPOCH)
    .ok()
    .and_then(|elapsed| i64::try_from(elapsed.as_millis()).ok())
    .map_or(Timestamp::UNIX_EPOCH, Timestamp::from_unix_millis);

After

// Direct construction for current time:
let timestamp = Timestamp::now();

// Or convert from an existing SystemTime:
let timestamp = Timestamp::from(some_system_time);

Before & After (ToolId, CapaabilityId, and GlobalName)

Before

// Only inherent methods were available:
let tool_id = ToolId::parse("promptforge/web/fetch")?;
let cap_id = CapabilityId::parse("promptforge/web")?;
let name = GlobalName::parse("promptforge/web/fetch")?;

// This standard Rust idiom DID NOT compile:
// let tool_id: ToolId = "promptforge/web/fetch".parse()?; // ERROR: FromStr not implemented
// let ids: Vec<ToolId> = raw_strings.iter().map(|s| s.parse()).collect::<Result<_, _>>()?; // ERROR

After

// Standard Rust type inference & parsing:
let tool_id: ToolId = "promptforge/web/fetch".parse()?;
let cap_id: CapabilityId = "promptforge/web".parse()?;
let name: GlobalName = "promptforge/web/fetch".parse()?;

// Seamless use with iterators and combinators:
let tool_ids: Result<Vec<ToolId>, _> = ["promptforge/web/fetch", "promptforge/fs/read"]
    .iter()
    .map(|s| s.parse())
    .collect();