epic: add spinner/status indicators for all long-running operations

[bug-ops]

Motivation

User-facing operations exceeding ~300ms should display status indicators via Channel::send_status() so users know what's happening. Currently only 2 of ~25 long-running operations show spinners (context compaction and summarization).

Existing Infrastructure

• Channel::send_status(text) — displays spinner with message; empty string clears it
• Channel::send_typing() — typing indicator (Telegram)
• Already used in context.rs:276 (compaction) and persistence.rs:114 (summarization)

Scope

25 operations identified across the codebase, grouped into 6 issues by subsystem:

Issue	Subsystem	Priority	Items
#1	LLM inference & provider warmup	P0	4
#2	Skills: install, registry, matcher	P0-P1	4
#3	Memory: init, embeddings, persistence	P0-P1	4
#4	MCP & external service initialization	P1	3
#5	Tool execution & web scraping	P2	4
#6	Miscellaneous: CLI, config, audio	P2	6

Implementation Pattern

let _ = self.channel.send_status("loading model...").await;
// ... long operation ...
let _ = self.channel.send_status("").await; // clear

Constraints

• send_status requires &mut Channel — some call sites may need threading changes
• Status text should be lowercase, concise (e.g. "loading skills...", not "Loading the skill registry, please wait")
• Clear status ("") after every operation to avoid stale messages
• Ignore send errors (let _ =) — status is best-effort