feat: add character count to pagination footer

[George-iam]

The pagination utility (src/utils/pagination.ts) splits large MCP tool outputs into pages. The navigation footer currently shows "Page X/Y" but does not indicate how much content is on the current page or the total content size. Adding a character/word count (e.g., "Page 2/5 (12,340 chars, 47,200 total)") would help the agent decide whether to request the next page or skip it.

Relevant files:

• src/utils/pagination.ts — modify the paginateSections function's footer generation
• test/pagination.test.ts — add tests for the new footer format

Acceptance criteria:

• Pagination footer includes character count for current page and total
• Existing pagination tests still pass
• At least 2 new tests verify the character count in the footer
• npm test passes